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NEC visualization, optimization and sweeping toolThe 4nec2 tool is a windows- and Nec-2 or Nec-4 based tool for both the starting and experiencedantenna modeler that can be used to create, view and check your antenna geometry structure andgenerate, display and compare near- and far-field radiation patterns. Also SWR, input impedance,F/B- and/or F/R-ratio for a range of frequency's on a linear or logarithmic graph (or Smith-Chart) canbe displayed.Furthermore an optimizer and sweeper is included. With this optimizer you are able to optimizeantenna- and/or other environment-variables for Gain, resonance, SWR, efficiency and/or Front toBack ratio. With the sweeper you are able to graphically display the effect of changing one or moreantenna- and/or environment-variables for a specified range of values/frequencies.

For the starting antenna-modeler a graphically based 3D geometry-editor is included which requiredno additional NEC knowledge while still enabling you to create and visualize current-distribution,far/near-field patterns and Gain/SWR charts. To be able to use one of both optimizers or the sweeper, some basic knowledge about the NEC syntaxis required. So one is able to (textually) create NEC based geometry structures and know somethingabout the results when using GN, EX, LD, and FR cards.

Although this help-file might look comprehensive, this is not directly related to the complexity of the4nec2 package but much more to the large amount of features available. Considerable effort wastaken to get used to 4nec2 without the need to first read the complete help-file.

The 4nec2 tool consists of four general forms/windows: Main, Geometry, Pattern, Line-chart plus anEdit-, Matching-, Smith-chart and an Optimizer/Sweeper form. Each form contains a menu bar withmenu-options. Most of these menu-options speak for themselves. Try out each of these menu-optionsand see what the results are. However there are some options who are more difficult to understand.These options are discussed in more detail further on in this help file. To get specific (contextsensitive) help for a certain window/form just push the F1 when the form/window is on-top.

When the 4nec2X eXtended version is installed the real-time 3D-viewer is also available for use.However this version requires a more modern computer-system and graphics-card.

In all the forms you can process the general buttons F1 to F12, Ctrl+O and Ctrl+Z / Esc. Thesebuttons, for which also a menu-option is included in the 'Main' form, have the following meaning

F1 Display this help file

F2 Select Main form

F3 Select Geometry form

F4 Select Pattern form

F5 Select Line-chart form

F6 View or Edit (4)nec2 input data

F7 Start NEC-engine and Generate new output data

F8 View NEC output-file

F9 Start/select 3D-viewer form

F10 Start Matching form

F11 Display Smith-chart form

F12 Optimize or Sweep variables

Ctrl+O Open (new) input file

Ctrl+S Save output file (as)

Ctrl+Z Exit program (also ESC may be used)

Some entry points to other Help information:

Nec-2/4 reference Variables and constants Modeling guide-linesValidate structure Current-sources (EX 6) Wire loading (LD 5)LC-Traps(LD 6) Wire coating (LD 7) Auto-Segmentation Ground types MiniNec ground (GN 3) Using NGF filesPropagation prediction gnuplot Plotting program Program SettingsWire table Genetic Algorithms DBW and dBuV conversionCapture/Print Troubleshooting About 4nec2

The 4nec2 help file contains so-called context–sensitive Help, making it possible that when using theF1 key in a particular window or form, help-text describing that particular window/form is displayed.

For easy reading the content of the 4nec2 help-file is also available as a (rich)text file. To print this file,open and print the file “4nec2.rtf”, located in the “..\4nec2\exe” folder, in your Word or Wordpad texteditor.

Other recommended sources for NEC related informations are the Nec-2 and Nec-4 user-manuals andthe excellent collection of antenna-modeling articles by L.B. Cebik (W4RNL), both available on theinternet. You can further read the _GetStarted.txt text-file included in the 4nec2 package.

The use of this 4nec2 software package is for own risk and the author of it cannot be held responsiblefor any faulty results or damage resulting from the use of this software.

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Main form F2 Show general data

In this form the general data, as listed in the 4nec2 input- or NEC output-file, is displayed. When theoutput-file is not yet generated, only few fields are filled.

After the 4nec2 program is started, by default, the last loaded Nec2/4 file input-file is re-opened.This file represents the data you are working with. This data is used to generate near- of far-fieldpatterns and may also used by the optimizer. Using File -> open you are able to choose and open another *.nec input-file. You are also allowedto select and open *.ant (antenna optimizer) or *.ez (Eznec) type input-files which are automatically converted to 4nec2 type input-files. To support the starting antenna modeler, in version 5.3, a graphical based 3D ‘Geometry editor’ was included. The benefit of this editor is the fact that it is now much more easy to create/modify antenna structures. On the other side however, using this kind of editor, it is not possible to specify symbolic information as used by the optimizer/sweeper. For further information about using and selecting between the available types of editors, see Edit . It is furthermore possible to specify an output-file. If this is the case, the program displays the data present in the output-file, but it is not possible to generate new data or use the optimizer. This option is useful to compare intermediate output file data if saved with a different name.

Please note that all numbers used in 4nec2 use the dot as the decimal seperator, independent ofwindows regional settings on the computer. So, especially for European users it is important to use thedot (.) instead of the comma (,) when entering decimal numbers.

Voltages and Currents specified and/or listed in the 4nec2 program use effective values. These arederived from the maximum values as listed in the NEC output-file by multiplication with 0.707.

Furthermore the voltage- and current-values displayed and the field-strength values shown for theNear- and Far-field-pattern are in accordance with the input-power specified in the ‘Settings’ menu-baroption. For further info about this, see the ‘Input-Power’ paragraph in Settings.

With the menu-bar on this form you have access to the most important 4nec2 options and features.

With the Calculate -> Generate NEC data command it is possible to start the NEC-engine andgenerate new NEC output data. With the Calculate -> Optimize design command you can start the4nec2 optimizer to optimize data made available through the 4nec2 input file Use Calculate -> Matching networks to let 4nec2 automatically calculate L, Pi or T matching networksto create an 1:1 match and determine the losses for the selected network.

With the ‘Show -> voltage sources’ or ‘show-> RLC loading data’ option it is possible to view detailedvoltage source or RLC loading data, including SWR, delivered or dissipated power.

Note however that if only two (connected) voltage sources are specified in the input file, it is assumedthat a split voltage source is used. In the general data on the ‘main (F2)’ form and the impedance/SWRdata on the ‘line-chart (F5)’ form the impedances and voltages are added. This is not the case of onlyone or more than two sources are specified.

Using ‘File -> Import’ one is able to import OpenPF or tab/white-space delimited far-field pattern data. This to let 4nec2 visualize the imported far-field pattern.For a further description about the OpenPF format see Pattern For an example of a tab/white space delimited far-field text file, open the file named

‘FarFieldImportExample.txt’ file in your ‘..\4nec2\plot folder’.Such a text file contains one or more sets of full/3D far field data. Each set is preceded by a line prefixed with a # and containing the text ‘Frequency’ with a numeric frequency value.After this a number of Theta sets are listed (from 0 to 180 degrees), each containing the gain values for a full 2D horizontal/Phi pattern (0 to 360 degrees).If (during import) an optional frequency, theta or phi angle is specified, the set for this specific entry is filtered out. Else the first/only set is loaded.

Geometry builder

Using the ‘Run -> Geometry builder’ menu-bar command one can start the ‘Geometry builder’. This isa powerfull tool to automatically create complex geometry structures using ‘auto-segmentation’ and/or‘equal-area rules’. To merge one or more structures to an existing model, open both the created *.nec and your 4nec2 fileusing Notepad and cut/paste the required cards/lines into your model. To remove overlapping wires,use ‘Geometry-edit’, select and remove wires one by one or select more wires by dragging a rectanglearound them and remove them as a whole.

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Geometry form F3 Show structure geometry

In this form, the structure geometry (including voltage sources, transmission lines, (wire)loading andpatches) as defined in the input file or as generated in the output file is displayed. With the cursormovement key's or mouse you can rotate and shift the structure. With the page-up/down buttons youcan zoom-in/out on the structure. When currents display or far-field pattern display is on these buttonszoom in/out on currents or far-field pattern. Other options are available as both keyboard-buttons andmenu-bar options.

When no NEC output file is available the background is displayed in a none-white color, and somemenu-bar options are disabled. When an output file is generated the data in this output-file isdisplayed. The background color is changed to white. The menu bar options are enabled according tothe data in the output file.

After editing the input file (by pressing F6), initially the (modified) input file data is displayed(none-white background). This is done so you directly can see the modifications you made to the inputfile. To see the resulting output file data you first have to generate a new output file by pressing theGenerate (F7) key.

You can switch between I(nput) and O(utput) file view by pressing the ‘I’ or ‘O’ button when theGeometry form is on top.

Wires/segments with a tag-number of 9800 or above are not displayed. This way it is possible to usefar-away dummy wires while the main structure is still visible with normal scaling. Structure validation(see below) is also not performed on these dummy wires.

You may left-click on any wire or segment to select a wire/segment and view additional information. To‘reset’ click anywhere else on the form. If a wire/segment is selected and the right mouse button ispressed, the ‘wire/segment’ pop-up menu is displayed. One useful option in this menu is the ‘center’option. With this option you can set the rotation center for the structure on the middle of the selectedwire/segment. With ‘reset’ you reset the center to the origin for the Y,Y,Z axis.A selected wire is displayed in blue color with a filled and an open black circle. The closed circle isend-1, the open circle is end-2 for the selected wire.

A further special and important option, which requires more explanation, is the “Validate” menu-baroption. This option can be used to manually or automatic validate the most important NEC segment-and geometry-requirements. When the output-file view is active more segment checks are availablethan with input-file view. For a further description of what kind of checks are performed see Validate.

Automatic Geometry-checking is done before each Nec-run. Automatic Segment-checking is alwaysdone after the Nec-run. Because of the time-consuming nature of the Geometry-checks, one canenable or disable automatic geometry-checks, using the “auto geo-check” menu option on the“Geometry (F3)” form. Segment checking is always active.

Further geometry validation can be done using “Show -> Open ends”. With this you you can check foropen ends. Using “Show->Junctions” you can check for the number of connected wires at junctions. And last but not least you can use the “3D-viewer” to validate your structure. This viewer shows allwires with their real radius. This way it is very easy to see if certain wires intersect or not. At junctionswith short fat segments you should check if a segments ‘volume’ does not lay more than about 1/3 inanother segments ‘volume’.

Under the ‘Show’ menu-bar option the following log-data is available:

- Last NEC input Pure Nec 2/4 input data which was send to the NEC engine for last run.

- Auto-segm log Logging about geometry modifications made by the auto-segmentation process- Step-rad log Logging about geometry changes made by stepped radius correction process- Symbol conversion Intermediate values for converted and calculated symbols/variables

The near- and far-field menu-bar options are only available if an output file is loaded which containsnear- or far-field data, generated with the RP- or NE/NH card or by using the Generate (F7) command.You can toggle the display for the near/far-field on or off with the menu-bar option or with the“R”(adiation) button.

When far-field display is enabled you can use the ‘far-field’ menu-bar option to let 4nec2 colorize thefar-field pattern using gain/magnitude, tilt/phase, axial ratio or sense data from the output-file.

With the “<” and “>” key's it is possible to switch between the different hor/vert/total or X/Y/Z patterns.If there are multiple patterns selected on the “Pattern (F4)” form for comparison, these key's are usedto switch directly between the far-field patterns for the different NEC output-files.

Under the 'wire/segment' menu bar option you can 'walk' through al the structure wires/segments,select a specific wire/segment and display the wire geometry (input file) data or the segment current inpolar or cartesian notation (output file). It is also possible to select a wire/segment by clicking with themouse on or near a wire/segment.

When the display of current-distibution is enabled, and also a freq-sweep calculation was performed,the function of the cursor/arrow key’s is changed from structure movement/rotation to frequency‘movement’. Using the left- and right arrow key’s one can ‘walk’ through the frequencies included in thesweep and inspect the change in current-disribution over the structure while changing the frequency. Tip: for optimal display of current-distrubution with changing frequencies it’s recommended to usecurrent- instead of the default voltage-sources. See Edit.’ for more info about specifying excitationsources. One can perform a frequency sweep by specifying a start-, stop- and step-frequency or by specifying alist of frequencies included in a text file. See ‘Generate’ for more info about this subject.

Use ‘Currents->Multi color’ and ‘Currents->Incr./Dec. Log-factor’ to visualize current distribution forsmall currents over gridded surfaces and/or large external structures.

You can use the ‘Plot’ menu-option to create and/or print linear 2D gnuplot graphs for one, more or allcurrents in the geometry structure.

Use the ‘File->Print’ to capture and print/save the geometry structure or other forms or windows.

The 4nec2 tool was initially developed to assist on wire-geometry structures and the display of(arbritrary shaped) surface patches is not that sophisticated. For instance the current on patches arenot visualized (yet), also structure validation is only performed in a limited way for patches.Rectangular, triangular and quadrilateral patches are displayed according the specified XYZ-coordinates. For arbritrary shaped patches a square shape is assumed. However not alwaysappropriate, this will give you well enough information about if center-, normal-vector and/orpatch-area data are correctly specified.

Under ‘Show -> Povray’ you may select between the generation of a true 3D geometry or far fieldpattern povray file.

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Validate Validate geometry structure

The Validate menu option on the Geometry (F3) form is used to check a large number of NECrequirements concerning the geometry structure and segmentation. With this, there are two differenttests to distinguish:

* Geometry checking/validation* Segment checking/validation

Because the “Geometry check” (especially for models containing a large number of wires) can takesome time, model validation is split into two different tests. Geometry validation is (optionally) performedbefore each Nec-run, Segment validation is automatically performed after each Nec-run. With ‘set autoGeo-check” on the Geometry form you can enable/disable automatic geometry checking.

After a geometry-check with errors and/or warnings a report-log is displayed. After a segment-checkwith errors a message is displayed. To get a report-log for the segment-check, manually run asegment-check. After each test all wires/segments subjected to warnings or errors are displayed ingrey and red colors. Use the left mouse-button, to select a wire and get specific segment error/warninginfo for the selected wire/segment.

Geometry-check validates the below:

1) Crossing or unconnected segments.

This error condition occurs when the distance between two or more segments is belowseg-length/1000 and the connection point is not a wire-end or a segment junction.

2) Intersecting wires/segments.

This warning is generated when the volumes of two or more wires are intersecting at a point otherthan their wire ends

3) Sharp angles or too short/thick segments.

This warning is generated when the intersecting volume of two or more wires, connected at theirend-points or segment-junction becomes too large.

4) Overlaid wires

This error condition occurs it two or more wires are overlaid (same end-points)

5) Unequal segmentation for parallel wires.

This warning is generated if parallel wires within 1/20 wavelength distance and having an ‘overlap’length of more than 1/10 wavelength have unequal segmentation.

6) Vertical/horizontal wire height below xxx.

This condition occurs when the height of one or both of the end-points for a certain wire goes belowthe limit as specified by its direction and the use of reflection coefficient or sommerfeld/nortonground.

Note however that above warnings (or even errors) do not say that your model is not usable. Theymerely inform you about where extra attention might be needed to improve accuracy.

Segment-check validates the below:

(L = segment length, R = segment radius, wl = wavelength, A=area)

Run segment-checks ‘9’ Generate error/warning report and view log-file

Show all seg-checks ‘0’ Show results of all below checks.

Warning(gray) Error (red)Segment Length ‘1’ Check segment length L > wl / 10 L > wl / 5 or L < wl / 1000Segment Radius ‘2’ Check segment radius R > wl / 100 R > wl / 30Segm. Len / Rad ‘3’ Check length/radius (def.) L < 8 * R L < 2 * R

(EK) L < 2 * R L < 0.5 * R Junc. L big / L small ‘4’ Check length at junction - L1 < 5 * L2Junc. R big / R small ‘5’ Check radius at junction R1 > 5 * R2 R1 > 10 * R2Junc. Len / Rad ‘6’ Check len/rad at junction L < 6 * R L < 2 * R

Surf-patch area ‘7’ Check max patch-area Error when : A > (wl*wl)/25

EX/LD requirem. ‘8’ Check EX/LD requirements

Furthermore the 3D-viewer is also extremely usefull for further analyzing and detecting crossing,intersecting and/or overlaid (fat and short) wire-segments (at sharp junction angles).

Additional validation for the geometry structure is possible by performing an Average-Gaintest or Convergence test

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Pattern form F4 Show far- or near field pattern

In this form the far- or near-field pattern data is displayed.

Far-field display

If far-field data is requested, the far-field is displayed in a polar diagram. You can select betweenlinear- or the ARRL-style (semi-logarithmic) scaling. When scaling is in dB’s, by default the ARRL-styleis set to let the minor lobes be more distinguishable. When scaling is in V/m linear-scaling is set andrecommended for use.

With the arrow-key's you can 'walk' through the different Phi- or Theta-angles. When calculations for arange of frequencies are asked (frequency sweep), the left- and right-arrow keys are used to 'walk'through the frequency range.If the ‘display far-field option’ is enabled on the ‘Geometry (F3)’ form, the selected pattern ishighlighted in the complete 3D drawing. Selections made on the ‘Pattern (F4)’ form are reflected onthe ‘Geometry’ form.

When clicking on or near the far-field pattern line, the far-field data (angle and gain/field) for this pointis displayed. Click anywhere else on the form to clear this data.

With the 'Home' key you can select one of three normalization types (logged in the upper left) whenviewing far-field Gain-data.

Using the 'compare' option (‘Insert’ and ‘Remove’ key’s) you can compare far-field radiation patternsfor two or more previously generated output-files. You may add a total of 5 different far-field patterns.You can also remove a pattern and add a different one. The only thing you must keep in mind is thatthe number of theta- and phi-steps for the patterns to compare must agree.

With the '>' or ’,’ and '<' or ‘.’ keys you may cycle through the different far- or near-fieldcolumns/patterns as included in the output file data. The default pattern for the far-field is the 'Totalgain' pattern. Using ‘Far-field->Show Multi pattern’ you can display all patterns together.

To show the circular polarized components RHCP- and, LHCP gain or E (left) and E (right) for thefar-field pattern, check the ‘show circular polarization’ option on the ‘Settings’ menu and use the ‘<’ or‘>’ keys to cycle between the circular polarized components, or use the ‘M’ key to show allcomponents using a Multi-pattern view.

With the 'G'(eometry) key or ‘Show -> structure’ option you can include structure geometry in the near-of far-field pattern display. Try the other menu-bar options to see what action they perform.

For information about beam-width, nr of lobes, max-gain and/or front to back ration you may enterthe ‘I’(nfo) key or select ‘show -< info’. Also the ‘J’ key or ‘show->indicator’ may be usefull to get additional information. This indicator is also displayed if you click on or near the pattern-line.When one or more patterns to compare are loaded and ‘information’ or ‘indicator’ is enabled, the ‘<’ and ‘>’ keys are used to select between the different loaded patterns.

Use the ‘OpenPf’ menu bar option to import or export far-field data using the OpenPF file format. This way one is able to exchange far-field data between 4nec2 and for instance Eznec or AO. This way could also store (export) generated far-field patterns for later usage, by importing it into another or similar model. Using the ‘FFtab’ menu bar option one is able to generate an Eznec style FarField table. One (requested) usage for this could be to import the far field table into a program like Tant.exe for

calculating Antenna Temperature and G/T ratio data. For further info see http://www.yu7ef.com/LowTemperatureAnt.htm

You can use the ‘Plot’ menu-option to create and/or print none-polar 2D or 3D far-field graphs usingthe gnuplot program.

Near-field display

If near-field data is requested, the near-field data is displayed in the XY, XZ or YZ plane. You canselect a specific Z, Y or X position with the left of right arrow-keys. You can set the active display planewith the 'spacebar'. When pressing the Page-up and Page-down key's you can switch between this 2Dview and a line-chart view in which the field-strength is displayed as function of the X, Y or Z position.In the 2D view you can select the vertical X, Y or Z position for the graph with the up- and down-arrowkey's

When displaying near-field data points on or in close proximity of the geometry structure this mayresult in a large maximum field strength value for certain field-points. This will also result in a largedifference between the minimum and maximum field-strengths values, resulting in a low‘color-resolution’ for the near-field display. To avoid this, two options are available. First you can'remove' field-points with field strength above a specified value. This is done with the 'Del' key in thepattern window. The second option is to set the linear field strength scale to a more (anti) logarithmicscale. This is done with the <Alt> and <page-up> or <page-down> keys. For both options alsomenu-items are included in the pattern form. These changes will also affect the display of the 3Dpattern on the geometry form.

The default ‘pattern’ for the near field is the 'E/H Total' pattern. This 'E/H Total' pattern is not included in the output file data, but is computed as the 'sum' of the E/H(x), E/H(y) and E/H(z) fields. With the '>' or ’,’ and '<' or ‘.’ keys you may cycle through the different near-field patterns forE/H(x), E/H(y), E/H(z) and E/H(total).

This ‘total pattern’ is calculated as below (as discussed by L.B.Cebik): Ex, Ey, Ez = magnitude given in peak volts/m or peak amps/mPx,Py,Pz = phase angle of Ex, Ey, Ez Cp = Ex*Ex*cos(2*Px)+Ey*Ey*cos(2*Py)+Ez*Ez*cos(2*Pz)Sp = Ex*Ex*sin(2*Px)+Ey*Ey*sin(2*Py)+Ez*Ez*sin(2*Pz)Tp = Cp*Cp+Sp*Sp Etot = Sqrt ( 0.5 * (Ex*Ex+Ey*Ey+Ez*Ez+Sqrt(Tp) ) ) Furthermore keep in mind that the data as shown in 4nec2 is presented in RMS volt/m or RMS amp/m and based on the power level set in the ‘Settings’ menu.

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Line-chart form F5 Show impedance, SWR and gain graphs

This form is used to display the input impedance, the SWR and, if specified, the gain, front-to-back(F/B) and front-to-rear (F/R) ratio as function of frequency- or variable-change on a line-chart. Theform contains valid information if a frequency-sweep is requested with the Generate (F7) command orwhen a Sweeping-action (F12) was performed.

When the charts are too rude, try a smaller frequency/sweep step-size. If this is not possible you cansmoothen the curve, by letting 4nec2 do a cubic-spline interpolation on the graph. Note however thatthis option can introduce considerable errors when the curve goes steep op or down, so increasing thenumber of calculation steps is recommended. Use ‘View->Smooth’ or the “O” key to smooth the curve.The maximum usable number of steps is set in the ‘Settings’ menu on the ‘Main’ form.

Use ‘Show -> Log X-scale’ (“F” key), to switch between linear and logarithmic frequency/variable axisscaling. Use ‘Show -> Log Y-scale’ (“L” key) to switch between linear and logarithmic Y-axis scaling.Initially after a frequency- or variable-sweep the R-in, Z-in and SWR graphs are set to logarithmicscaling. The others default to linear scaling. If values pass the Y=0 line, like when X-in is changingfrom inductive to capacitive, the chart can not be set to logarithmic scaling.

You may click anywhere on a graph to let 4nec2 display additional X,Y value information. Use theleft/right arrow key to move the selection.

The form can be resized by dragging the window-borders. Try the menu-bar options to see what actions can be performed on the graphs.

With the ‘Tab’ key you can select one or both of the Graph windows for changing the scaling orswitching between Linear or Logarthmic (if possible).

Impedance and SWR information is also available on the Smith-chart (F11) form.

Note: If two (connected) voltage sources are specified in the input file, it is assumed that a splitvoltage source is used. In the general data on the ‘main (F2)’ form and the impedance/SWR data onthe ‘line-chart (F5)’ form the impedances and voltages are added. This is not the case of only one ormore than two sources are specified.

If more than two voltage- or current sources are specified use ‘V/I source -> previous/next’ to switchthe SWR- or Impedance-plot from one source to the other.

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Edit F6 Enter/modify or delete 4nec2 input data

With this function you can view, enter or modify your 4nec2 antenna input-model. With version 5.3.0and later can select between three different kind of entry systems, so called ‘editors’ to use: TheNotepad-, NEC-based- or the graphically-based geometry editor. You select between one of theseeditors with the Settings menu-bar option. When pushing the F6 function key (or using Edit->Input fileon the Main(F2) window) the selected editor is started and available for entering or changing yourantenna-model/geometry-structure With version 5.6.5 a fourth editor, based on the old NEC-editor was added. You can select betweenbelow four types of editor:

Notepad edit

Nec-edit (old)

Geometry-edit

Nec-edit (new)

The drag-and-draw style ‘Geometry-editor’ (or the new NEC-editor) is especially suited for the startingAntenna-Modeler, whereas the experienced NEC user may prefer ‘Notepad-’ or the old styleNEC-editor.

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Notepad edit

This is the ‘traditional’ (4)nec2 windows-editor, which lets you directly modify the (4)nec2 input-file.When using this editor it is presumed the user has good knowledge about the NEC-syntax, becauseno syntax checking is done. On the other side this delivers maximum flexibility to use any kind ofNec-card and/or symbolic- and equational data.

One important difference between this Notepad- and the other editors is the fact that theNotepad-editor requires closing (or saving) the new data, before the NEC-engine can be run. Theother editors can stay active when performing a NEC calculation (F7 key).

To create new 4nec2 input-files using Notepad, Open an existing NEC-file, edit it and save it using adifferent name. If done, use again the ‘open’ command to load the newly created file.

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Geometry edit

This drag-and-draw style geometry editor graphically supports the user in drawing/moving/rotatingwires and placing sources, loads and transmission-lines. The user is guided in selecting between theavailable source-, load- and ground-types. Pre-defined wire-radius, wire-conductivity andground-parameter settings are available and one can select between metric, feet, inch or wavelengthbased length and/or radius units.With this editor however it is not possible to specify symbolic (and equational) data to be used withinthe optimizer/sweeper. This due to the drag-and-draw based nature of the editor.

See Geometry-edit below for further help-information.See Menu-bar functions for a listing of available functions.

n.b. If someone has suggestions for a general usable algorithm to convert 3D numerical wireend-coordinates to a SYmbol based lay-out, to be used by the optimizer/sweeper, please let me know.

Despite numerous thoughts about this I did not yet succeed in finding an acceptable solution.

However; in version 5.4.0, a first try was done to write the output of the Geometry editor to thecorresponding *.nec file using symbols(variables) which then could be used by the optimizer toimprove the model. Select ‘Options -> Write symbols/variables’ in the ‘Geometry-edit’ window to switchbetween default NEC syntax and 4nec2 symbolic syntax. Use ‘distinguish XYZ coords’ to avoid usingthe same symbol for both X,Y and/or Z coordinates when they are the same value.

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NEC editor (old)

This text-based NEC-syntax aware editor guides the user when entering or changing 4nec2input-data. In contrast to the above editor, no pre-defined radius, conductivity or ground specificationsare available, but it is throughout possible to include symbolic- and equational-data to be used withinthe optimizer or sweeper.

With this editor the selected GW, LD or EX card in the Edit window is highlighted on the Geometrywindow. If a wire is selected on the Geometry window, the corresponding GW line is highlighted in theEdit window. Any (wire)changes made in the Edit-window are reflected on the Geometry windowwhenever the current row on the Edit-window is changed

You may select one or more lines to be used for cut, copy and/or paste. Pressing SHIFT and clickingthe mouse or pressing SHIFT and one of the arrow keys (UP ARROW, DOWN ARROW, LEFTARROW, and RIGHT ARROW) extends the selection from the previously selected row item to thecurrent row. Pressing CTRL and clicking the mouse selects or deselects a row in the list. You can alsouse copy/paste to copy and/or paste (using the clipboard) between the NEC-editor and othertext-based NEC-(input)files.

To add a new NEC card, use ‘new line’ and select the required card-type from the ‘card’ combo-box.When selected use the <TAB> key to fill the next fields for the selected card-type. When field-entry isdone, use up/down-arrow to add the new card-data to the list of NEC cards. As long as the card-datais not added to the list it is possible to change the card-type. Once added to the list it is not directlypossible to change the card-type. To do so, first delete the current card-line/row.

While editing you do not have to save your data first to see the Nec results. Just click the “Calculator”button or push <F7> to run the NEC-engine using the current data as displayed in the Edit window.Once you are satisfied (or not) you can save your data (or not) using ‘File->Save(as)’

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NEC editor (new)

Because I didn’t like the old style Nec-editor, I decided to create a new spreadsheet styleNec-editor. For the moment the new Nec-editor is only Nec2 compatible, however in the nearfuture Nec4 support will be added. For those using 4nec2 together with a Nec4 engine it’ssuggested to use the Notepad editor or the old style Nec-editor.

You can select the new style Nec-editor on the Main (F2) window by using ‘settings->Nec edit(new)’.

You can start the editor by using the F6 key (or select ‘Edit -> Nec input-file’). After this a newwindow should show up containing multiple Tabs, some with an Excel style grid and some withordinary text- and/or drop-down boxes. To navigate around between the individual cells in theExcel style grid, use the up/down/left/right arrow keys or directly select a cell using your mouse.

When navigating between cells, the help-text box (just below the menu commands) is updated foreach new cell.

This new Nec-edit window will show you below Tab pages:

Symbols

On this page you can specify and/or modify all Symbols (variables) used in your model. At thebottom of this page you can select between different scaling methods. Scaling does affect thedata on the Geometry page and all symbols used on this page. When ‘custom’ scaling is selectedone can enter a user specific scaling factor. Note that you may also specify symbols to be usedon the ‘Source/load’, ‘Frequency/Ground’ and other Tab-pages.

Note: when using already existing Nec input (example) files it’s possible that one or more SYvariables have been re-used (defined more than once). These (position dependent) SY variablesare mostly defined just before they are used in multiple GW, LD or EX lines. A warning messageis generated when saving such a file.To avoid unexpected results using the new Nec-editor, these files (which have been created withthe Notepad- or old-style Nec-editor) need some slight modifications so that all used SY variablesare unique throughout the Nec input-file.

Geometry

The Geometry page does contain all data used to specify the model’s geometry structure. On thefirst column (named ‘type’) you can select between the different geometry types:

Wire, to specify a straight wire containing the specified number of segments

Helix, to specify a helical or spiral structure built from straight line segments

Arc, to specify a circular arc built from straight line wire segments

copy/move, to move and/or copy one or more of the preceding geometry lines

rotate, to rotate preceding geometry lines to create a cylindrical structure

mirror, to mirror the structure in X, Y and/or Z-plane to benefit from symmetry

arbitrary shaped surface-patch, to specify an arbitrary surface with known area

triangular sp, ditto for a triangular shape

rectangular sp, ditto for a rectangular shape

quadrilateral sp, ditto for a quadrilateral shape

patch continuation, to specify a string of rectangular/quadrilateral patches

multiple (rectangular) sp, to cover a rectangular region with a number of rectangular patches

To specify tapered wires, both in segment-length and/or in wire-radius, check the ‘use wiretapering’ box. If checked, additional columns for straight wire rows will show up.

Source/Load

Using the check-boxes at the top of this page, one can specify additional antenna structure datasuch as:

Excitation sources; at least one source, mostly a voltage- or current-source, is needed to getuseful output-data

Wire/RLC loads; used to specify wire conductivity, trap/RLC loads or wire insulation. You mayuse a single or multiple antenna materials.

Transmission lines; to model open-wire or coaxial feed/transmission lines. These areequational lines and do not contribute to the radiation pattern.

Frequency/Ground

With this page you can specify the environment in which the antenna is placed. A (design)frequency specification is required. When no ground is specified, free space is used. If the antenna is placed above none-perfect ground, one can use the drop-down boxes to selectbetween different ground types. Select ‘user-specified’ to manually enter specific groundconditions. Check ‘use ground screen’ to model an additional radial wire ground screen.Check ‘use second ground’ to model a two-stage ground as on a hill-top or near a cliff or (salty)beach. Others

This page is used to enter more specific Nec2 data. You may (un)check ‘Ground connection’ ifyou would like to have your wires with an end at Z=0 to be connected or isolated from ground. The ‘Read/Write geometry’ box is used to read or write predefined geometry structures. There’s no harm in always using the ‘extended kernel’

Comment

To provide your model with additional comments, use this page.

Menu-bar commands

On top of the Nec-edit window a number of menu-bar commands are available. Most of them willbe familiar to the average computer user, however some require additional explanation. Underthe ‘Cell’ menu-option, cut/copy/paste commands are available for editing a single cell. Under the‘Rows’ menu-option, cut/copy/paste commands are available for editing multiple rows at once.

Under the ‘Selection’ menu-option commands are available to perform certain actions on anumber of selected cells. To select one or more cells, hold down left mouse-button and dragaround over the cells you would like to include in the selection. Or click on the upmost row orleftmost column to select a specific column or row. After a selection has been made you can use‘make same value’, ‘add same value’ or ‘multiply same value’ to treat all selected cells the sameway. Use ‘make same value’ to enter equal values in all selected cells. Use ‘add/multiply samevalue’ to add or multiply existing cell values with a second user supplied value.

Use ‘Options->Auto update geometry window’ to let 4nec2 automatically update the Geometry(F3) window after each change. However if a complex structure is specified using large number ofgeometry lines this updating could become irritatingly slow. If this is the fact, uncheck themenu-bar option.To let 4nec2 automatically resize column-widths when window size is changed, check the‘autoresize columns’ option.

You can individually change column widths by clicking and dragging the column separator bars onthe upmost row (containing the header names). These settings will be saved, so next time whenNec-edit is started, your column widths will be restored.

Command buttons

Two command buttons have been placed on the Edit window. From right to left, a Save buttonand a Calculate button. The Save button saves all changes to the current file (as doesFile->Save). The Calculate button does start a new Nec calculation using actual data, whether ornot this data is saved before. If you don’t like the outcome resulting from latest changes you canquit the edit window without saving.

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Geometry Edit

This editor is used to specify the antenna structure like creating a (schematic) drawing. In the editwindow a 2D or 3D-view of the antenna input-file geometry is displayed which can be modified usingselect-, draw- and drag/drop methods.

To switch between 2D and 3D view, select one of the four leftmost view-mode buttons labeled “3D”,“XZ”,”YZ” or “XY” on the upper left of the Edit-window. For 2D view you can switch between XZ, YZ orXY plane.

Next three buttons are used to Add, Select or Delete (new)wires orsource/load/Tr-line objects.

The rightmost seven object-buttons are used to select the kind of object on which you want to performan edit, create or delete operation. These objects are devided into two groups. A first group with bothdrag/drop- and textual-edit capabilities and a second group with only textual-edit capabilities. Wires,Sources, Loads and Transmission-lines belong to the first group. Comment, Frequency andGround-parameters belong to the second group.

Select, Add or Remove (new) wire(s).

Select, Add or Remove voltage/current sources.

Select, Add or Remove RLC/Wire-loading, LC-traps or Wire-coating.

Select, Add or Remove transmission-lines.

Add or modify comment or edit wire-data on spread-sheet form

Enter or modify design frequency or select ‘thin-wire’ kernel.

Add, modify or remove ground specifications.

When viewing a structure or modifying none-wire objects you may use either 3D or 2D view. Whenmodifying Wire-geometry it is advised to use only the 2D-view to avoid unexpected results. Thisbecause when moving a wire in 3D-view it automatically connects to the nearest available wire. Toundo a faulty movement, use the right mouse-button while the mouse-pointer is over the selected wireor use the ‘edit’ menu.

To select between metric, feet, inch or wavelength as the length/radius units use the ‘Settings’menu-bar option in the “Main” window.

Modify existing objects

To modify an existing object, select the type of object (wire, source, load, etc...) by clicking thecorresponding top-row object-button. If a none drag/drop-type object is selected the correspondingdata is directly available on the right part of the edit-window.

When a ‘drag/drop’ type object is selected you will also have to select the desired object from therange of similar objects by clicking on the appropriate item in the 2D or 3D picture or by using thescroll-bar on the mid-right part of the screen.

If an object is selected the wire or segment on which it is located is highlighted and the mouse-pointerchanges from the default arrow to a two- or four-point arrow, indicating that the object is ready formoving. The corresponding object data is available for textual editing on the right of the screen. If atwo-point arrow is visible, the whole wire is movable. When a four-point arrow is visible only one end ismoved.

Note: When modifying a drop-down-list or a text-box-value, enter the <Tab> key, click another text-boxor anywhere inside the picture-box to let 4nec2 know that the value has changed and the model canbe repainted.

In 2D-view, wires can be moved to any other 2D position. According to the “Snap to grid” or “Snap towire” check box setting, the moved wire-end(s) ‘snap’ to the nearest grid-position or to another nearwire-end. When a wire is moved in 3D-view it always automatically connects to the nearest wire. The‘snap’-range for ‘Snap-to-wire’ corresponds to roughly half the grid-line spacing. When a wire is selected the wire is displayed with a green and red open or filled box on either side ofthe wire. The bleu box represents end-1, the red box end-2. A filled (blue or red) box indicates that thiswire-end is connected to one or more other wires. (positive NEC current flows from end-1 to end-2, soin the direction of end-2. Think about the ‘red’ end-1 as the back-light of a car).

To release connected wires or to keep them connected while moving, (un)check the “Keep connected”check box within the wire-data. This option is also in effect when modifying the XYZ end-position,length or theta/phi wire-data text boxes.

When a two- or four-point mouse-pointer is visible one can use the right mouse-button to performadditional edit operations. It is possible to connect or disconnect a certain wire-end by using theright-mouse button while the mouse-pointer is over a selected wire-end. “Disconnect end” or “Connectto near wire” are only available when the mouse-pointer is over a certain wire-end. Most other actionsare available if a certain wire is selected.

When the mouse-pointer is not located over an object (default pointer visible) the right mouse-button isused to shift the whole picture up/down or left/right.

Sources, Loads and Tr-line(ends) can only be moved from one wire/segment to another wire/segment.They automatically snap to a near segment. The ‘snap-range’ for this equals half the grid-line spacing.

Add new objects

To add new objects, select the “Add” button. The mouse-pointer changes to a cross-hair indicating“Add” mode is active.

When object-type “Wire” is selected (2D view), click inside the picture-box to set end-1, hold down thebutton, draw the wire and release to set end-2. By default the third (depth)dimension in the 2D view isset to zero (highlighted text-box on right side of screen). You may modify this value to create objectsfor other ‘depth’-coordinates.

Use “Options->Hide wires not in plane” to draw overlapping or almost overlapping 2D- structures fordifferent ‘depth’-coordinates (for instance cubical quads). This will avoid selecting the wrong wire and

new or moved wires do not accidentally connect to wires lying in another ‘depth’ plane.

When a wire is created or the length for a wire is changed the number of segments is automaticallyupdated according the specified “Set segmentation” option. You can select between “low”, “medium”and “high” segment-count in the “Options” menu-bar option, corresponding to 10, 25 or 100 segmentsper half/wave. When a whole wire is moved the number of segments is not changed.

To avoid updating the segmentation when wire length is changed, select/check “Stop segmentation” inthe above menu. This could be (temporary) usefull when a precise segment-count was alreadyspecified due to short wires/sharp bents

If the (design)frequency for the model is changed the segment-counts are not automatically updated.Use the “Recalculate segm.” option to let 4nec2 recalculate the segmentation for the selected wire(s)according the specified segmentation density and new frequency. (use Ctrl+A to select all wires).

When creating new wires, it is not strictly needed to position the mouse-pointer on the exact XYZcoordinates. After having drawn (part of) the required structure you may select a wire and use theend-1 or -2 edit-boxes on the right part of the window to specify more exact coordinates. Use theend-1 or -2 option-boxes to specify which wire-end should stay in position. Use the ‘Keep connected’box to specify whether other connected wires should stay connected or not after modifying thewire-data.

The default radius used for new wires is made equal to the radius specified for the last added/createwire (available wire with the highest wire-number). When adding the first wire to a new model, thewire-radius is explicitely asked for. Use “Snap to grid” to place wire-end coordinates relative to thespecified grid. Use ‘Snap to wire’ to automatically connect a moved wire-end to another nearbywire-end. To add a source- or load-object, click the desired object-type button, click anywhere inside thepicture-box to create a new source/load object and drag the source/load onto the desiredwire/segment using the left mouse-button. When done, edit the source/load data on the right part ofthe screen to select between different source/load types and to specify additional source/load data.

To add a Transmission-line object, click the Tr-line button and click on the desired wire/segment to setend-1 of the new Transmission-line. Hold down the left mouse-button and move onto the secondwire/segment to set the other end-2 of the new Transmission-line. Edit the data on the right part of thescreen to set char-impedance, line length and/or crossed line.

To create/modify ground parameters use the right-most button and select between free-space or theother available ground-types. To specify a linear or radial cliff, select the “second/far ground” box tospecify additional ground data.

Use the “Create” menu to create rectangular-, grid-style-, circular- or helix-type shapes. Using the‘circle’ option you can also create triangles, squares and other n-sided structures by specifying anumber of sections of 3 or 4 or more. You can create wire-arcs by deleting one or more wires from aprevious created circle.

Selecting multiple wires

To select multiple wires for moving, deleting, copying or pasting click anywhere near a wire, hold downthe left mouse-button and move the ‘selection-box’ over the wires to select. When 3D view is activehold down the <Shift> key to avoid rotating the 3D structure. To add distinct wires to the currentselection, use the <Ctrl> key while selecting other wire(s). When in 2D view it is sometimes possiblenot all selected wires are visualized (red color), because one or more wires may overlap each other.

A selection of multiple wire always contains a ‘main’ wire. This wire is displayed as a more thick line

with a green and red open/filled box on either side. To move a selection of multiple wires, locate themousepointer over this ‘main’ wire till the mouse-pointer changes to a 2-point arrow. When no previouswire was selected the ‘main’ wire is the first of all selected wires. If a single wire was previouslyselected the selected wire becomes the ‘main’ wire.When moving multiple wires the complete selection is snapped to a grid-point or nearest wire indicatedby the end-1 or end-2 of this ‘main’ wire. To ‘snap’ for a certain end, click near the required end whenmoving is started.

When having selected one or more wires you can use the right mouse-button to perform additionalactions.

One special operation is the “Rotate and Move” action. With this operation (similar to the original NECbased GM card) you can rotate and/or move selected wires or you can create one or more similarstructures, for instance to create a stack of yagi’s. When using the rotate and move operation, it isimportant to keep in mind the order of transformations. First, all selected wires are rotated around theX-axis for the specified amount of clockwise degrees followed by rotation around the Y-axis, followedby rotation around the X-axis. Finally the resulting structure is moved according the specified X,Y,Zdistances.When the ‘Create N new structures’ option is selected, each new structure is created with the selectedor previous created structure as the reference for the next transformation.Another operation is “Rescale wire(s)”. This operation is used to scale all selected wires to a newfrequency or by a specified scaling-factor. This scaling involves both wire length/coordinates andwire-radius.

Two important things to keep in mind using above operations is the fact that the “Keep connected”check-box is not in use (unselected but connected wires are not moved) and these operations canonly be undone by performing ‘reverse’ operations.

To rotate a certain wire around one of his ends, first move the end to the center of the XYZ-axis, do therotation and then move the wire back, or directly edit the the Phi/Azim or Theta/Elev text boxes on theright part of the screen. If the latter action is performed, bu sure you selected the correct “Fix end-1” or“end-2” check-box.

You can use the “Resequence trag-nr” operation to renumber the tag-nr’s after creating, cutting,copying and/or pasting one or more wires.

Tip: Use the 3D-viewer together with the Geometry-edit function and meanwhile switch between bothwindows to see the immediate 3D results when changing wire lengths, posistions and/or radius. Thisto avoid overlaid or intersecting wires.

Spread-sheet wire-table edit

Another way to modify Wire-data is by selecting the “Wire data/Comment” object-button. All wire datais displayed in a spreadsheet like grid for textual editing. You can select, remove, delete cut and/orcopy one or more wires to get the wire sequence that suits your needs. You can also cut and/or pastetextual (wire) content to or from another document.

You can use the operations in the “Edit” menu to perform similar actions on one or more selected cells,rows or columns. For instance to change wire-diameter for the whole or part of the structure or set thesegment-count to user required values.

Other

Select the “Show Nec” menu-bar option to see the corresponding NEC cards and to become used to

the NEC syntax. Use “Options -> Write symbols/variables” to switch between default NEC andsymbolic 4nec2 syntax.

To create a new design, use “New” from the “File” menu. This will clear the drawing and reset all data.Before starting the drawing it is required to enter the ‘design frequency’. This will also initialize thegrid/axis-size according the specified wavelength.

While editing you do not have to save your data first to see the Nec results. Just click the “Calculator”button or push <F7> to run the NEC-engine using the current data. Once you are satisfied (or not) youcan save your data (or not) using ‘File->Save(as)’

Some shortcut-key’s:

W show/hide wire-nr X set YZ planeT show/hide tag-nr Y set XZ planeE show/hide ends Z set XY planeS show/hide segments 3 set 3D view

<Home> Reset view<Page-up>/Page-down> Structure zoom in/outShift + <Page-up>/Page-down> Grid zoom in/out<up>/<down>/<left>/<right> Rotate 3D view

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Menu-bar functions:

FileNew Clear screen and create new modelOpen Open other existing model/input-fileSave Save current modelSave as Save current model using another nameExit Exit editor without saving changes

OptionsSet square picture Resize window so circular structures are shown circular.Show struc/wire loading Toggle the visualization of wire- and structure loading.Hide wires not in plane Hide overlapping wires when in ‘Add-mode’Set segmentation Set low, medium or high segmentation (for new/changed wires) Stop auto-segmentat. Do not recalculate when wire-length(s) is/are changedRedo segmentation Redo (exact) segmentation for selected wires in structureTAB as fieldseparator Use <Tab> as field separator when saving model to fileWrite symbols/variables Use symbols(variables) when saving model to fileDistinguish XYZ coord. Use different symbols for X,Y or Z coordinates of same (abs)value

Edit (wire-model view)Connect closest wire Automatically connect selected wire-end to closest wire.Disconnect end Didsconnect selected wire-end from attched wire(s).

Split wire Split selected wire into 2 or more sub-wires.Reverse wire Reverse end-1 and end-2 of selected wire.CeNter at wire Center window at middle of selected wire.Rescale wire(s) Perform rescaling for one or more selected wiresRotate/move wire(s) Rotate and/or move one or more selected wiresSelect All Select all wires for the modelCopy wire(s) Copy one of more selected wiresPaste wire(s) Paste previously cut or copied wires

Cut/Delete wire(s) Cur or delete one or more selected wiresResequence Tag-nrs Renumber all tag-numbers starting with 1.Undo delete Undo previous delete for one or more wiresUndo Move Undo previous move for one or more wires

Edit (spread-sheet view)Rotate / Move Wire(s) Rotate and/or move wires for one or more selected rowsInsert wire Insert new row/wireDelete wire Delete current wireMake &Same value Make selected cells, row(s) or column(s) all same valueAdd same value Add specified value to selected cell(s), row(s) or column(s)Multiply same value Multiply selected cell(s), row(s) or column(s) with value.Cut Cut one or more selected rows/wiresCopy Copy one or more selected rows/wiresPaste Paste previously cut pr copied rows/wires

CreateRectangle Let 4nec2 create a rectangular structureRect-grid Let 4nec2 create a rectangular gridded structureCircle Let 4nec2 create a circular structureHelix Let 4nec2 create a helical structureRadials Let 4nec2 create some radials

Show Nec View how the current model would be saved in textual format. Segm-info View wire- and segment info.

Notepad- and Nec-edit

The default/minimal lay-out for a simple 4nec2 input file is the following:

Zero or more CM (comment) cards.One CE (comment end) cardOne or more GW (wire geometry) cardsOne GE (geometry end) cardOne FR (design frequency) cardOne or more EX (excitation point) cardsZero or one GN (Ground condition) cardZero or more LD (loading) cardsOne EN (end of file) card

You may include comment in the input file used by 4nec2 by using the ' character (single quotationmark) anywhere in the input file. See also the example files on your 4nec2 home-folder.

You may also hide specific (far away) wires in your geometry structure by using tag-numbers in therange 9800-9900. This way the model initially might be more correctly scaled. Don’t specifytag-numbers above 9900, because these tags are internally used by 4nec2 to model Current-sources.

To use the built-in 4nec2 Current-source Excitation-type see Current-sources (EX 6)

To use the built-in 4nec2 LC-trap Loading-or Wire-coat loading type see LC-Traps (LD 6) and Wirecoat (LD 7)

For additional ground- and/or wire-loading data see Ground conditions or (wire) loading

All text after the first EN card is ignored, so you may use this area for temporary cutting and pasting ofNEC cards.

With version 5.7.0 and later it’s also possible to enter the position of Voltage/Current sources (EX),Spot-loads (LD) and Transmission lines/Networks (TL/NT) on the wire in percents from the beginning(end-1). You do this by entering a value from 0 to 100 followed by a percent (%) sign. 4nec2 will automaticallyconvert this percentile distance to the required segment-number. Note however that the moresegments a wire consists of the more precise the positioning will be related to the specified percentilevalue.

For those who are not yet familiar with the NEC syntax and/or antenna modeling, there are a lot ofrecommendable articles, written by L.B. Cebik (W4RNL), available on the internet.

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EX 6 Specifying Current Sources

Besides the use of the standard NEC Voltage Sources (EX 1), 4nec2 also supports the use ofCurrent Sources. To make this work, the standard NEC type for the EX card is extended with anadditional type 6 specifying a current source. When using a text editor as the 4nec2 entry systemthe fields for this card are the same as those for the voltage source, however the real andimaginary parts are specified in Amperes

When using the ‘geometry editor’, current-sources are automatically created when ‘Current’ isselected as the excitation source type.

Internally in 4nec2 this EX type 6 is converted to a voltage-source on a dummy segment andconnected to the initial segment through a network NT-card. To see the results of the internalcurrent- to voltage source conversion, use ‘Show -> Nec 2 input’ on the ‘Geometry (F3)’ windowafter a (4)Nec2 calculation is done or select the ‘show Nec’ menubar option when using the‘geometry editor’.

Mostly the default Nec voltage-source (EX 0) is used. When modeling with multiple sourceswhere the current for each source requires a specific phase relationship, the use ofcurrent-sources (EX 6) is needed.

Split sources

When two sources are specified on two nearby and connected segments, a so called split-sourceis assumed. Such a split-source is usefull to specify a source on a segment junction, such ascould be used for an inverted-V antenna. Furthermore split-sources are very usefull to preservesymmetry when a GX card is involved. This to minimize calculation time.

For a split-source impedances and voltages are added on the ‘Main (F2)’ and ‘Line-chart (F5)’windows. This to represent a single source.

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LD 6 Specifying LC-Traps

Together with the use of the standard NEC Loading types from LD1 to LD5, 4nec2 also supportsthe use of the LC-Trap loading type. To make this work, the standard NEC type for the LD card isextended with an additional type 6; specifying an LC-trap. The fields for this card are the same asfor the parallel/Series RLC card, except for the R(esistance) field. For the LC-trap this field (F1)represents the unloaded–Q of the inductor. A zero in this field defaults to a unloaded-Q of 100.

When using the ‘Geometry’ editor you can select ‘LC-trap’ after adding a new or selecting anexisting RLC-load object. The corresponding LD card is automatically created.

When using a text editor as the 4nec2 entry system the LD 6 card has the below syntax:

Cmd Tag-nr Start-seg End-seg coil-Q L (in H) C (in F) [fr]LD 6 2 1 16 16 5.5e-6 45e-12

Internally in 4nec2 this LD-type 6 is converted to a parallel-RLC loading type. For calculating thecoil loss-resistance (which depends both on coil-Q and the reactance X of the coil) the designfrequency from the nec input-file (First FR card) is used to get to coil reactance. Optionally you can specify different frequencies to use for reactance- and thus loss-calculation foreach coil/trap.

Internally in 4nec2 this LD-type 6 is converted to parallel-RLC loading type using the frequencyvalue as specified on the initial FR-card. To see the results of the internal LD conversion, use‘Show -> Nec 2 input’ on the ‘Geometry (F3)’ window after a (4)Nec2 calculation is done or selectthe ‘Show Nec’ menubar option when using the ‘geometry editor’.

You may also specify the start- en end-segments as a percentile distance (0 to 100) from thebeginning of the wire.#$K

LD 7 Specifying Insulated wires (Wire-coating)

Besides the default NEC Loading types from LD1 to LD5, 4nec2 also enables you to specify datafor the insulation wrapped around conducting wires. This insulation produces shortening effects inthe specified wires, thus lowering the velocity factor. To make this work, 4nec2 uses an extra LD7type.The method used in this was described by L.B. Cebik in ‘www.cebik.com/amod/amod83.htm’l

When specifying insulated wires, there are two radii of interest. First the radius of the conductingwire (as specified in the GW card) and second the radius of the wire plus insulation. Thedifference between both values is the thickness of the insulation layer. Furthermore the dielectric constant for the insulation material is of interest. In 4nec2 a highinsulating effect (very low conductivity) for the material is presumed.

On the internet the below dielectric constants were found:

Aluminium-oxide 10Bakelite 3.5 - 4.5Copper-oxide 18.1Glass 5.0 - 9.0Glass (window) 7.6Mica 4.0 - 8.0Neoprene 4.0 - 6.7Oil 1.5 - 4.7Paper 1.6 - 2.6Parrafin 2.0 - 3.0Pertinax 4.3 - 5.5Plexiglas 2.6 - 3.5Polycarbonate 2.9 - 3.2Polyethylene 2.4Polyamide (nylon) 3.4 - 3.5Polystyrene 2.4 - 3.0Porcelain 5.0 - 6.5PVC (hard) 3.0 - 4.0

PVC (soft) 4.0 - 5.0Rubber 2.7 - 3.2Shellac (Nat.) 2.9 - 3.9Styrofoam 1.03Teflon 2.1Water (destil) 34 - 78Wood (dry) 1.4 - 2.9

Most plastics appear to have a dielectric constant (permittivity) between 2.0 and 3.5. Thedielectric constant of air is around 1.0, so if we would specify a value of 1.0, no matter whatradius we would get the performance of bare wire.

When using the ‘Geometry’ editor you can select ‘Coat’ after adding a new or selecting anexisting RLC-load object. The corresponding LD card is automatically created.

When using a text editor as the 4nec2 entry system the LD 7 card has the below syntax:

Cmd Tag-nr Start-seg End-seg Diel-const Coat-radius (mtr)LD 7 2 1 16 2.8 .003

The parameters ‘Tag=nr’, ‘Start-seg’ and ‘End-seg’ are the same as the correspondingparameters used by the LD 0 through LD 5 command’s.You may also specify these start- en end-segments as a percentile distance (0 to 100) from thebeginning of the wire.

The first floating point parameter ‘Diel-Const’, specifies the dielectric constant for the insulationmaterial used. The second floating-point parameter specifies the overall radius for the wire plusinsulation.

Internally the LD7 command is converted to an LD2 command using the below equation:

L = 2e-7 * (diel * R/r) ^ (1/12) * (1 - 1/diel) * Ln(R/r)

L Value for distributed inductance in Henry/meter

diel Dielectric constant (as specified in the LD7 command)Ln Natural LogarithmR Radius of of wire plus insulation (as specified in the LD7 command)r Radius of wire (as specified in the corresponding GW command)

This equation is especially suited for dielectric-constants between 2 and 3.5, the normal range ofinsulation materials used by radio amateurs.

To see the results of the internal LD conversion, use ‘Show -> Nec 2 input’ on the ‘Geometry (F3)’window after a (4)Nec2 calculation is done or select the ‘Show Nec’ menubar option when usingthe ‘Geometry editor’.

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GN 3 Specifying MiniNec type ground

When ‘connecting’ wires to a Real (SomNec)- or Finite (Fast)- ground (using a Z-value of zero)the reported antenna impedance is usually unpredictable. To avoid this, use Real/SomNecground with an elevated radial system or, when using verticals, use the MiniNec ground type.

When computing far-field data the MiniNec ground takes into account the ground conductivity anddielectric constant at a distance. However, when computing currents and antenna input-

impedance it consideres the ground to be perfect. (as could be the case using a nearly perfectburied radial system).This ground system however is only valid when the antenna structure does not contain horizontal wires below 0.2 wavelength. This mostly restricts the use to vertical antennas. When modeling other antenna types, use an elevated radial system together with the Real/SomNec ground type. (see http://www.cebik.com/ for more info about this subject).

The MiniNec ground type is available through the “GN 3” extension on top of the default “GN –1” to “GN 2” default NEC command set.

When using a text editor as the 4nec2 entry system the LD 6 card has the below syntax:12 Cmd I2 I3 I4 Diel-const Conductivity3 GN 3 0 0 0 14 0.00645 Internally in 4nec2 this GN-type 3 is converted to a combination of perfect ground (GN 1)

and a second circular cliff ground-medium (GD 0 0 0 0 diel cond). This second groundmedium starts at a distance zero from the antenne and also has a height of zero.

67 To see the results of this internal GN conversion, use ‘Show -> Nec 2 input’ on the

‘Geometry (F3)’ window after a (4)Nec2 calculation is done or select the ‘Show Nec’menubar option when using the ‘geometry editor’.

89

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Using a Numerical Green’s Function file (NGF)

10 Numerical Green Function files (NGF) are used to split a nec-based geometry structure inone or more a static reusable part(s) and a dynamic part. As the static part for instanceone could specify a number of different refelctor screen’s while the dynamic partdescribes the radiator. Both parts are created using standard nec input-files.

1112 For the first file, the static part, the structure is pre-calculated, thus generating a so called

NGF file. This NGF file is created by adding a ‘WG’ card to the nec input-file. 1314 In the second file, containing the more dynamic part (e.g. the radiator) a card is added

which specifies to import/include the pre-generated NGF file. This file is ‘imported’ byusing the ‘GF’ card.

1516 Mostly the (first) input-file creating the NGF file contains far more geometry cards than

the file using the NGF file. Because the NGF file is pre-generated, (re)calculation theoverall structure will much more time efficient.

1718 The frequency and ground-settings to use must be specified in the first file, producing the

NGF file. The second file which uses the pre-generated NGF file may not contain any FRor GN/GD cards.

1920 When using Numerical Green's Function files (NGF) some considerations must be taken

into account.2122 Using the Nec2dXS*.exe engines it's possible to explicitely specify the name of the NGF

file to use. The following syntax applies:23

24 To create a NGF file : WG file.ext25 To use a NGF file : GF file.ext2627 'file.ext' can by any file-name like 'ngf.nec' or 'screen.ngf' or 'refl.ngf'. When no NGF

file-name is specified the name defaults to 'NGF2X.NEC'. These files are placed in your'..\4nec2\exe' folder.

2829 When a NGF file-name is specified it's also possible to use the 'Print table of coordinates'

flag. The following syntax applies:3031 To print a coord-table : GF 1 file.ext32 Don't print coordinates : GF 0 file.ext3334 Furthermore note that when using/importing a NGF file, 4nec2 is not able anymore to

automatically detect the specified number of segments from the *.NEC input-file. To let4nec2 select the appropriate nec2dXS*.exe engine it is needed to manually set the totalnumber of segments.

3536 This is done with 'Setting -> Nec-engine -> Min-nr segments'. You can enter a value just

above the total number of segments specified in both *.nec files. (the one generating theNGF file and the one using the NGF file)

3738 Also because ground parameters are specified in the binary *.NGF file and thus are not

directly available through the second *.NEC file it is required to use an appropriate GE(-)1 or GE 0 specification in the second *.NEC file so 4nec2 knows if it has to generate ahalf (180 degree) or a full (360 degree) far field pattern.

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Symbols Declaration of symbols/variables

41 In version 4.0 and later versions, variables, also known as symbols (especially for those usingAntenna Optimizer by Brian Beezley) were introduced.

4243 With this feature you can assign a certain numeric value or numeric expression to a

(character) variable. For instance you may set the variable 'len' to 20, and use this variableanywhere in your 4nec2 input-file where you want to specify a length of 20.

4445 This is done by including a special card in your 4nec2 input file with the “SY” identifier. For

instance, if you want to specify a length of 20, a height of 10 and a width =0.1, you specify thefollowing:

46SY len=20, hgh=10, width=0.1

47 You have to include the SY card before using the variable in one of the succeeding NECcards.

4849 Furthermore you may include expressions/equations when declaring variables. For instance: 50SY len=10, height = 5+10*len ‘ Height is 5; increased with 10 times length

51 Valid operators in these are + , - , * , / and ^ 52

53 You may also include functions like sin", "cos", "tan", "atn", "sqr", "exp", "log", "log10", "abs","sgn", "fix", "int" and "mod". For instance:

54SY ang=60, len=20, lenX = len*cos(ang), lenY = len*sin(ang)

55 Or even5657 SY dist=30mm, diam=1.3mm, Z0 = 276 * log10 ( (2*Dist) / Diam)585960 Standard scientific precedence rules apply. If they must be overruled you can use brackets.6162 Below operators are also included, however I did not yet find any real use for it:63"and", "or", "not", "xor", "eqv" and "<", ">"’, "<=", "<="

64 You may divide your variable declarations over one or more SY cards. The SY cards can beincluded anywhere in your input file as long as the variables are declared before they areused. You can then use these variables and/or equations in any NEC card you should like.

6566 Variable declarations have to be separated by comma's (",").6768 A couple of fixed pre-defined identifiers are also included. They are: 69cm (centimeter)70 mm (millimeter)71 in (inch)72 ft (feet)73 pF, nF, uF, nH (pico-, nano and micro Farad)74 nH and uH (nano- and micro Henry).

75 Note that the variables and identifiers are not case sensitive.7677 When variables are used in two or more 4nec2 input-files it is possible to declare them only

once in a separate definition-file. Use ‘Settings -> predefined symbols’ to view, add ,delete ormodify these predefined symbols. This file could be used to declare, for instance, AWG # wiregauges, your default ground parameters and/or wire conductivity values.

7879 Prefdefined variables (constants) can be ‘overwritten’ in ‘SY lines’ in the 4nec2 input file.

80 Remark: Please do not use the above mentioned pre-defined identifiers or functions as SYmbol namesbecause this will lead to unpredictable results.

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Modeling guide-lines8182 Although most of the below described guide-lines are (automatically) checked when loading or

generating new output-data or by using the structure validation option it is suggested to keep thebelow modeling guide-lines in mind when creating new or modifying existing models.

Wire modeling8384 Len = segment length

85 Rad = segment radius (diameter/2)86 WL = Wave Length8788 1) Positive current flows from end-1 to end-2

2) len < WL/10 for accuracy in most caseslen < WL/20 in critical regions89 len < WL/5 on long straight segments

90 3) Avoid extremely short segments (len < .0001 WL)

4) ‘rad’ must be small relative to ‘len’ and ‘WL’

91 rad < len/2 with default thin wire kernel92 rad < 2*len with extended thin wire kernel93 rad < len/10 default usage

94 5) Avoid - Large changes in radius, especially on short segments

Sharp bends in thick wires

6) Wires that are connected must contact at segment ends(connection separation < len/1000)

7) Use equal source segment length and lengths for segments next to source

8) No voltage sources (EX 0) or loads at wire open ends

9) Use same segmentation for close parallel wires.

9) GE (Geometry End) usageGE 0 : No ground (free space)GE 1 : Ground plane present, ‘touch’ wires (Z=0) are connected to groundGE -1 : Ground plane present, ‘touch’ wires (Z=0) are insulated from ground

Wire grid modeling

1) Grid-size is not too critical (appr. WL/10 at midband)

2) Len/rad not critical (10 < len/rad < 30 goor for wires attaching surface)

3) Minimize ‘len’ and ‘rad’ changes (<2:1) at connection pts of wires and surfaces

4) Use denser gridding (2*) at connection points of wires and surfaces

5) Also acceptable for thin structures (plates, wings, etc)

6) Try two segments/side

7) Not usable for surface charges or currents

Surface patch modeling

1) Make sure surface is closed and not too thin (no plates, fins or wings)

2) Maximim patch size may not exceed 0.2 * 0.2 WL

3) Corners are defined using right hand rule.

4) Avoid long thin/narrow pathes

5) Large patches on smooth surfaces, smaller ones on curved areas

6) Currents are defined at centre only, so not good for edge currents

8) When wires are connected they must do so at patch centers

9) Use ‘wire-grids’ where edge connections are needed. - Wire grid equals surface if mesh is ‘small enough’- Problem:

- can’t afford real fine meshes (*- Sparse meshes have too much L, not enough C

- Possible solutions:- negative L distributed loading- fat, rod-like wires

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Calculate F7 Generate NEC output-data

This general option is used for generating new NEC output-data.

If one of the below described options is selected, first of all, 4nec2 pre-processes the active *.nec inputfile to remove all comment and to solve the variable- and constant definitions. The resulting intermediatefile, containing pure NEC input-data is placed in the “\out” folder with the *.inp extension. When this isdone, the Nec-2 or Nec-4 engine is started and the *.inp file is red by the engine to generate new NECoutput-data. This output-data is placed as an *.out output-file in the “\out” folder. When all calculationsare done 4nec2 open this output-file and the results are displayed on the F2 to F5 forms.

When a Sommerfeld-Norton ground is specified, 4nec2 automatically generates or copies theappropriate ground file to be used by the Nec-2 engine. These ground files (with the *.gnd extension) arestored in the “\out” folder. If the requested file already exists, it is copied; otherwise a new one is createdwith the somnec engine. When using the Nec2dXS engine the SomNec data is calculated by the engineitself and the additional somnec engine and ground files are not required.

When the ‘Generate’ command-button is selected, a pop-up window is displayed with different options tochoose from.

The following generate options are available:

Use original file Run NEC-engine and generate new output from active *.nec input fileFar field pattern Run NEC and generate specified 3D far field pattern for input file

Full Generate full 3D far-field pattern.Ver. Generate vertical far-field pattern for specified phi angle.Hor. Generate horizontal far-field pattern for specified theta angle.

Frequency sweep Run NEC and request for calculations for a range of frequencies Gain. Run NEC and generate SWR and Gain graphs for specified phi and theta.Ver. Generate vertical far-field pattern for each frequency and SWR and Gain graphs.Hor. Generate horizontal far-field pattern for each frequency and SWR and Gain graphs.Full Generate 3D far-field pattern to get full Gain, F/B- and F/R-ratio data for graphs.

Near field pattern Run NEC and generate specified near field pattern

E-fld Generate near-electric-field data and show in 2/3D pattern and graph style. H-fld Generate near-magnetic-field data and show in 2/3D pattern and graph style.

360 degree Gain table Generate ItsHF 360 * 90 degree Gain-table for specified frequencyGain @ 30 frequencies Generate ItsHF 90 degree Gain-tables for 30 frequencies

Batch (button) To run multiple files as a single batch, see below.More (button) To define more settings.Visible when one of both ItsHF options is seleceted.

Use Original file

When this option is used, the 4nec2 input file is converted to default NEC format and send directly to theNEC-engine, without further modifications and/or additions. You can use this option for a quick first testafter creating a new nec file or to specify calculation options not supported by 4nec2.

When using one of the other (below) options it is recommended to remove all RP and NE/NH cards fromthe *.nec input file.

Far-field pattern

The most used calculation probably will be the default far-field pattern calculation. This patterndetermines in which direction you antenna system will radiate/receive best and in which direction signalis supressed. It may also be used for signal-coverage studies and interference-level analysis.

When the default far-field (full, horizontal or vertical) pattern is requested one must specify the resolutionto use. This resolution value defines the stepsize increments for the Phi/Azimuth and Theta/Elevationangles. When a ground(plane) is involved, only the upper halve of the ‘radiation-sphere’ is calculated. When lowresolution (< 1 deg.) is specified it is possible that the max-nr of field-points is exceeded. If so, use the‘ver’ or ‘hor’ option, or increase the max-nr of far-field points in the settings menu.

When running a Full/3D far field pattern, by default the radiation-efficiency and the Receiving DirectivityFactor (RDF) are also calculated and displayed on the Main (F2) window. RDF is specified as thedifference between (maximum) forward-gain of an antenna and the calculated average-gain of theantenna. For more info, see Radiation-efficiency. Note that when running a horizontal/vertical 2D pattern or when a surface-wave request is made, noradiation-efficiency is calculated.

On the middle-right of the window one can specify if an average-gain-test (AGT) should be performed.With this you can check if your antenna model is more or less a valid Nec2/4 model. See AverageGain-Test for additional info about the subject. Running an average-gain test is only possible if the full/3Dfar-field option (without surface wave) is selected.

Experienced NEC users can use the ‘expert’ button to set special far-field calculating options. Foradditional info about these ‘XNDA’ options, please consult the Nec-2 or Nec-4 user-guide. Default XNDAsettings are:

1: Ver/Hor/total field, 0: No normalization0: Power-gain2: Compute average-gain

If required, ‘Auto-segmentation’ or ‘Step-radius correction’ can be enabled through the ‘Setttings’ menu.

When the far-field option is selected, besides the Gain values the default E-field is calculated. If required,

one can check the “E-fld” box. If done so, one may enter a certain distance (in Km) for which the E-fieldis calculated. (Use “<” and “>” on the Pattern [F4] window to switch between Gain and E-field values).

By default only the space-wave and the ground-refelected wave are used for far-field calculations. Toinclude the surface-wave in the calculations, check the “Surf-wave” box. If this is used, additionalparameters are required:

- Max-Z Maximum height (meter) for which the far-field is calculated.- Dist Distance for which the far-field is calculated, mostly set to 1 Km

Frequency sweep

When a frequency-sweep is requested (starting with version 5.8.0) on can choose between two furtheroptions: a) Sweep by specifying a start- and stop frequency together with a fixed step-size (delta frequency)b) Sweep using a predefined list of frequencies. If this is required, the ‘from file’ box should be checked. Starting with version 5.8.0 one can let 4nec2 show you the change in current-distribution by ‘walking’throught the list of calculated frequencies. For futher info see the Geometry window. When an a) type frequency-sweep is requested, additional Start, Stop and Step-size data have to bespecified. Do not specify a Start (and Stop) frequency very much apart from the design frequency,otherwise certain NEC requirements, such as segments per wavelength, might be violated. To evaluate the performance over a wide range of frequencies you could consider using the Sweeperfunction with Auto-segmentation enabled. With the first option, called ‘Gain’ you must supply the Phi/Theta or Azimuth/Elevation Forward-angle forwhich a Gain-graph should be plotted. Because only one far-field point is calculated (that for thespecified direction) no F/B-ratio and F/R-ration data is available or displayed. To get F/B (front-to-back) or F/R (front-to-rear) plots; select one of the other options. Ver(tical)-,Hor(izontal)- or 3D-pattern. Using the ‘Ver’ and ‘Hor’ options, for each frequency step, a completevertical- or horizontal-pattern is calculated for the specified Theta/Elev or Phi/Azim angle. Furthermore the F/B and F/R ratio is calculated and plotted on the ‘Line-chart (F5)’ form. These ratiosare calculated for the selected plane. To get F/B and F/R-ratio calculated in 3D space (as generallyused), select the 3D option. Note that none-directional antenna systems don’t produce meaningful F/B- and/or F/R-ratio data. Note also that when using the ‘Full’ option only the whole 3D pattern for the last frequency-step isdisplayed on the ‘Patten (F4)’ form. This to limit the overall memory usage for the 4nec2 package. Tovisualize multiple patterns, select the ‘hor’ or ‘ver’ option. Use the arrow-keys to visualize the changing ofthe pattern (play-back) for the specified frequency-range. When specifying the main-beam direction the backward direction is automatically updated, according theselected option (ver/hor or 3D) and the free-space/ground-plane settings. You may overwrite thesedefaults manually with your own settings. When the b) type frequency-sweep is requested one can specify the list of frequencies to use byselecting ‘Settings -> pre-defined frequencies’ on the ‘Main (F2)’ window. Be sure to specify the list offrequencies with increasing frequency values, else you will get a somewhat corrupted ‘line-chart’ display.

Gain calculation

By default forward-gain is calculated as the single gain-value for the specified direction. F/B ratio iscalculated as the difference in gain between the forward- and backward-directions. The F/R-ratio iscalculated as the difference between the forward-gain and the maximum gain-value for the backwardhalf of the radiation pattern which is centered around the backward-direction.

To get more control over how forward-gain and F/B-ratio are calculated (especially usefull whenoptimizing) it is possible to specify delta-theta and -phi values for both the forward- andbackward-direction. If a none zero value is specified the gain over the specified region as defined by theTheta/Phi value plus or minus the specified delta value is averaged. The number of averaging steps isdetermined by the specified resolution.

Sommerfeld ground

When using the Real/SomNec ground in a frequency-sweep in conjunction with de default nec2d engine,the ‘negative conductivity trick’ is used, in which the Real/SomNec ground data is generated only oncefor all frequencies. However this Nec-2 behavour will generate less precise data.

To overcome this ‘problem’ one could use the Sweeper function and specify the frequency as a variableor you could select the enhanced nec2dXS engine. This modified Nec-2 engine recalculates theReal/SomNec ground data for each frequency-step, so precision is not degraded.

Troubleshooting

During generation of near/far-fields, frequency-sweep- or ItsHF-data, additional NEC card's are added tothe original *.nec input file. If error's are generated during calculation, you may inspect this temporaryNEC input-file by selecting ‘View -> Last NEC input’ on the ‘Geometry (F3)’ form, just after performingthe (failed) calculation. Use the F8 function-key to inspect NEC output-file data.

Near-field pattern

The field close to the antenna is called the near-field. This field is quite different from the far-field thatcharacterizes propagated electromagnetic waves. Near-field intensities are very usefull for EMI studies,RFI and TVI minimization or FR-hazard analysis.

In contrast with the far-field, the near-field is calculated over a 3D grid of points. Start, Stop andStep-size values for the three dimensions X, Y and/or Z have to be specified. Mostly a step-size of (Stop– Start) / 20 will be fine. You can select between the electric or magnetic component of the near field tobe computed.

Use the ‘test’ button to let 4nec2 automatically create start-, stop- and stepsize-settings for a 3D volumewhich includes the whole geometry structure. This to quickly create initial near-field patterns which canthen be used to further fine-tune the start-, stop- and stepsize settings.

ItsHF option

With version 5.6.0 and later a more user-friendly interface with the ItsHF software has been created. Thenew interface enables you to create two different types of ItsHF compatible Antenne input-files:

- Full 360 degree Gain table for sepcified/design frequency for the antenne under test (type 13)- Set of 2D gain tables for a specified Phi/Azimuth angle for frequencies from 2 to 30 Mhz (type 14)

Both types of antenna files (and other pre-defined ItsHF types) can then be used to createArea-coverage or Point-to-point plots. After the antenna files are created one can let 4nec2

automatically create 4 kinds of plots:

- Area-coverage map Plot showing propagation performance on a (partial) world-map.- Point-to-point time plot Chart showing propagation performance as function of time- Point-to-point distance plot Chart showing propagation performance as function of distance- Point-to-point graph plot Chart showing propagation performance as function of time and frequency

Above ‘propagation performance’ can be visualized using user selectable parameters like ‘Signalstrength at receiver’, “Signal to Noise ratio’, ‘Maximum usable frequency’ or ‘Radiation angle’

Besides transmitter- and receiver-antennas and -locations, the ItsHF propagation prediction softwarerequires additional settings to automatically create the requested plot. These parameters, settings andoptions are discussed under ItsHF propagation prediction.

To use the ItsHF software package it must be installed on your computer system. Use 'Settings ->Folders' to specify your ItsHF home folder.

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Batch mode

With version 5.4.1 running 4nec2 in batch-mode was added. This way one is able to run 4nec2 for acomplete set of 4nec2, Antenna-optimizer or EZnec input-files as a single batch of work.

To use this feature, Open the “Generate (F7)” form/window and select the required calculation option.After this, click the “Batch” button at the bottom of the window. If done so, a new “Batch processing”form/window is displayed. To add files to the list, select the required files using Windows-Explorer (withCtrl- and Shift key’s), drag them to the Batch-processing window (while holding down the left-mousebutton) and drop them onto the window. All selected files are now automatically added to the list of filesto process. You can add a single file using the “Add” button. To delete one or more files, select these filesusing the left mouse-button and click the “Del” button. To select (and delete) all files use Ctrl+A.

When all required files are added, click the “Start” button to let 4nec2 process all listed files. In thecolumn labeled “Status” the outcome of the calculation and geometry/segment validation is logged.

To (temprorarely) halt batch processing of input-files, click the “Halt” button and wait till the NECcalculations for the current file are done. If you think this will take too long, you can alternatively abort theNEC calculations by clicking/selecting the NEC-engine in the windows task-bar and clicking the closebutton of it. To resume batch processing use the “Start after last” menu-option.

When all files are calculated, depending on the “File -> Refresh 4Nec2 data” option you can move thefocus or double-click on any of the listed files to let 4nec2 immediately load and display the data for theselected file.

Click on the ‘File’ column-header to sort all file-names in ascending or descending order.

Batch processing can also be used to convert multiple antenna-optimizer (*.ant) or Eznec (*.ez)input-files into Nec based files.

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Command-line mode

With version 5.7.3, none-interactive command-line mode was added. This way one can start 4nec2 froma windows batch file (*.bat) and let 4nec2 read the specified 4nec2 input-file, pre-process the data, runthe Nec2/4 calculation engine and create a Nec output-file.

To create usefull far- or near-field data one must add his/her own RP, NE or NH command in the $nec2input-file to be used. One can use the ‘use original-file option’ on the “Calculate (F7)” to check the resultsof the RP, NE or NH card specified.

To use 4nec2 in command-line mode, create (for instance) a test.bat file (in the same folder where theinput-files are listed) and use below syntax:

“C:\4nec2\exe\4nec2.exe <file1.nec> -I”“C:\4nec2\exe\4nec2.exe <file2.nec> -I”“C:\4nec2\exe\4nec2.exe <file3.nec> -I”etc…

When the “-I” argument is not used, 4nec2 does start in ‘normal’ interactive mode with the specifiedinput-file.#$K

Auto-segmentation

When optimizing and/or sweeping antenna performance, it is likely that dimensions and/or frequenciesare changing, so it is possible that certain NEC requirements, such as the minimum number of segmentsper half-wave are not met any more. To overcome this problem, Auto-Segmentation is used.

If this feature is enabled (See Settings on Main window), each calculation/optimization/sweeping step,the wire length for each wire is checked against the actual wave-length and the specified number ofsegments per wire, and the position for voltage/current sources, RLC-loading and transmission lines isupdated.

If a certain number of segments is already specified in the input file, at least this number of segments isset with auto-segmentation. This to avoid auto-segmentation decrease the number of segmentsspecified for critical regions. If you do not want to specify a minimum, set the number of segments toone.

If the number of segments is preceded by a “+” sign the number of segments is fixed, meaning, thesegments for this wire are not affected by the auto- segmentation process.

When enabling the Auto-Segmentation feature, you are asked to specify the number of segments perhalf-wave. Although, mostly accuracy improves if more segments are specified, also the computationtime is increased. For ‘simple’ structures, without sharp angles, a value from 10 to 20 will be sufficient. Ifprecise impedance values are required or if wires joining at sharp angles are used more segments couldbe required. If you are not sure what amount to specify, please use increasing values and compare theresults. (You could do this using the Sweeper function). Also abrupt current changes on the structuremight indicate an insufficient number of segments. One place more segments aren’t better is if wires ofdifferent diameters are connected.

If computer performance is an issue, you could consider not to the use the auto-segmentation feature. Ifthis feature is disabled, the processing especially for large input files with many wires is speed-up.

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Step-radius correction

When modeling Yagis or other antennas with stepped diameter wires, 4nec2 can perform an automaticstepped radius (stepped diameter) correction.

If this feature is enabled (See Settings on Main window) a substitute element is created for each taperedone found (with certain restrictions, see “Tapering to perfection” by L.B. Cebik at www.cebik.com). The

substitute element has a uniform diameter and a length that yield essentially the same self-impedanceas the tapered diameter element. Thus, the substitute can be expected to behave--either by itself or inan array of elements--in the same way as the tapered element. All this to minimize inaccuracy whenusing large radius differences on a single element.

It does no harm to request the use of a stepped radius correction even in cases where the correction cannot be applied. However, this results in some unnecessary processing that will increase the total timeneeded for calculations so I suggest you not use StepRad except in cases where it is necessary.

The conversion program has a limitation in that it will not apply the correction to Yagi elements unlessthey are parallel to either the X or Y axis. Yagis that "point" in a direction other than a multiple of 90°azimuth, or Yagis that have been oriented for vertical polarization, will not be corrected

In case of problems using this option, please don’t hesitate to ask me for support.

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Average-Gain-Test

To check the reliability of your model, you can run an ‘average gain test’ (AGT). To run such a test, usethe ‘Generate (F7)’ command, select ‘Far field pattern’ and check ‘Aver-Gain test’. Then click the‘Generate’ button.

When the ‘expert’ button is selected and using the lowest option-box, one should select the ‘1 – averagegain’ option to perform this same test. (The other option-boxes could be left to 1:Ver/Hor/Tot field, 0: nonorm, 0: power-gain).

To get usefull test results 4nec2 automatically (temporary) removes all wire- and other resistive loadingand (if specified) changes the gound-conditions to perfect-ground when doing the required calculations.

The test-results are presented on the main (F2) form.

The following gradation can be made for the Average-Gain-Test results:

> 0.95 and < 1.05 Model is likely to be accurate> 0.90 and < 1.10 Model is usable for most purposes.> 0.80 and < 1.20 Model may be useful, but can be improved.< 0.80 or > 1.20 Model is questionable and should be refined.

When the resulting value is below 0.8 or above 1.2 the value is displayed in red color.

The db value between brackets can be used to correct the far-field pattern gain.#$K

Radiation efficiency

If ground-, wire- or other R(LC)-losses are involved, the value for ‘Radiation efficiency’ might be usefulldata.

Radiation efficiency is defined as the ratio of ‘pure’ radiated power to the antenne input-power.

This data is automatically generated and displayed on the ‘Main’ form when a full/3D far-field request ismade. When using the ‘expert’ one can manually decide between letting Nec2/4 calculate average-gainand thus radiation-efficiency data. To do so, set the lower option box on the ‘Generate (F7)’ form to “2:Radiation efficiency” .

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Open file Ctrl+O Open NEC input file

This general option is used to open another input (or output) file. You may specify an alternative folderor file-extension to search for. When opening the selected file, the program first try's to locate thecorresponding output file with the extension *.out. When such a file exists, this file is loaded and thedata is displayed on the Main, Geometry, Pattern and Line-chart forms.

When the default output file is not available, the *.nec input file is loaded, pre-processed andconverted to a *.inp file and the corresponding data is displayed in the Main and Geometry forms. ThePattern, Line-chart and Smith-chart forms are not available.

It is possible that the 4nec2 program generates an error when or after loading a default or temporaryoutput file. This is mostly the case if the output file is incomplete, because incorrect input file data isused. If this is the case, remove the *.out file from the “\out” folder, change the *.nec input file and tryagain.

When specifying an input-file with the '.ant' extension it is assumed you selected a AO (antennaoptimizer) or Nec-wires input file and you are asked if this file has to be converted to 4nec2 format. Ifconfirmed, most of the input data is automatic translated from AO/Nec-wires format to 4nec2 format.

However the following items must be checked for:

- The need to include the optional GX card when X-axis symmetry was specified.- Additional excitation and spot-loads when the GX card is included.- Excitation and spot-load placement on wire ends.

When specifying an input-file with the '.ez' extension it is assumed you selected an EZnec type inputfile and you are asked if this file has to be converted to 4nec2 format. If confirmed a new file with thesame name but with an “.nec” extension is created and opened. For as far as I (the author) am aware all Eznec files should automatically be converted without needingfurther (manual) corrections. On the internet, nec files with the slightly different Unix/Linux text-file format are available. If you wouldwant to load such a file, this format is automatic detected by 4nec2. If so, you are asked if this file hasto be converted to the default windows type text-file.

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Save file as Ctrl+S Save output file as

This general option is used to save the active output file data to an output-file with a different name.This option is useful for comparing different far field radiation patterns or if you want to savecalculation or optimizer results for later investigation. (Open file with *.out or other extension)

When comparing different far field patterns be sure these files are generated with the same Theta enPhi settings. If not, you won't be able to open these files.

If you want to compare optimizer results with manual generated results note that the optimizer onlycalculates far-field points for theta angles between 0 and 90 (ground) or 180 (free-space) degrees andthis is only done when a resolution unequal zero is set. If you are not sure which RP card settings are used for a specific calculation or optimization cycle,open the *.out output-file (F8 key) and look for the RP settings.

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Settings Modify user-, program- or memory-usage settings

The Settings option on the Main form is used to modify default-, user- or program- settings. Thesetting under 'memory settings' are program settings. The maximum values for these settingsdepend on you computer configuration.

The following settings are available:

Notepad edit Use windows default Notepad editor to edit input-fileNEC editor (old) Use old-style NEC-syntax aware editor to edit input-fileGeometry edit Use drag-and-draw style geometry editor to edit input-fileNEC editor (new) Use new-style NEC-syntax aware editor to edit input-file

Auto-Segmentation To enable auto-segmentation feature and specify nr of segmentsStep-radius corr. To enable stepped-radius correction.

Show circular-polar. Show circular polarization components E-left/right instead of E-theta/phi

Char-impedance To set the characteristic line impedance for SWR plot and Smith chartInput-power Input power used for voltage, current and field strength calculations

Phi/Azim unit To select between Phi/Theta and Elevation/azimuth usage.Length unit To select between meter, wavelength, feet or inch as length unit.Radius unit To select between millimeter or inch/Awg as radius unit.Predefined Freq’s To edit the list of fixed frequencies for a ‘from file’ frequency-sweep.Predefined symbols To edit your predefined SYmbols list.

Nec-engine:Nec2d engine Use Nec2d*.exe as NEC calculation engine (1)Nec2dXS engine Use Nec2dXS*.exe engine, especially for windows-XP systems (2)Nec4D engine Use Nec4D*.exe as NEC calculation engine (3)special engine Use special engine Manual select Use ‘min-Nr segments’ to select engine-‘size’ or specify Nec4

engine nameMin-nr segments To set the nec2d(XS).exe as selected by 4nec2 (see below)

Memory usage:max-nr fld-points Maximum nr of near/far field calculation pointsmax freq/sweep Maximum nr of steps for frequency/variable-sweep.max-nr LD cards Maximum nr of (wire) loading cardsmax-nr TL cards Maximum nr of transmission-linesmax-nr EX cards Maximum nr of excitation sourcesmax-nr 3D-points Maximum nr of points used in 3D-viewer (graphics memory)max-nr of SYmbols Maximum nr of SYmbols to use with optimizer/evoluter.

Optimizer settings:Absolute steps If selected use absolute steps else use relative stepsMax-initial step size Initial/maximum step size used for the optimization process in %Step size if optimizedStep size for which the optimization is considered to be ready in %

ItsHF settings:--- area coverage----- By default only the type-13 area-coverage antenna file is generatedCreate ‘Area’ input-file If selected create *.ICE/REC/VOA area-plot input file Calculate Area-plot data If selected create *.IG1/RG1/VG1 plot/data-fileShow Area-plot on screen If selected generate and show Area plot on the screen--- Point-to-Point ------ By default, only the type-14 point-to-point antenna file is

generatedCreate ‘Point’ input-file If selected create *.ICE/REC/VOA point-to-point input file

Calculate Point plot-data If selected create time/distance/graph plot-data fileShow Point-plots on screen If selected generate and show point-to-point plot on screen

--- engines-------------- Select predicion model/engine to useuse ICEPAC If selected, use ICEAREA/ICEPAC model for calculationuse REC533 If selected, use RECAREA/REC533 model for calculationuse VOAcap If selected, use VOAREA/VOAPAC model for calculation

Other settings:Rear segment size To specify the size of the rearward segment for F/R calculationWait for DOS-box If checked wait in calculation engine dos-box for Enter keyFast/(auto)redraw To select between maximum speed or automatic screen refreshLIN min. value Default minimum scale value for linear far field dB-scaleLOG min. value Default minimum scale value for logarithmic far field dB-scale

Folder settingsNotepad editor To set the path to Notepad.exe or other custom editorWordpad editor To set the path to Wordpad.exe or other custom editorItsHF folder To set the main/home-folder for the ItsHF propagation prediction

programgnuplot folder To set the main/home-folder for the ‘gnuplot’ plotting programNecWin+ folder To set the main/home-folder for NecWinPlus

Input power

The 'power' setting is used to compute the structure currents and the magnitude for the nearelectric and magnetic field. The effect is that the voltage for the voltage source on the EX card ismodified in such a way as if it would be perfectly matched and delivers the specified input-powerto the antenna structure. (Constant power mode, (multiplication with SQRT(specified_input_power / input_power_from_output_file)) If you would like to keep the originalspecified voltage in the EX card, please specify an input-power of 0 (zero) watts. (Constantvoltage mode)

Please note also that the Voltages and Currents specified in the 4nec2 program are effectivevalues, and not maximum values as used by the NEC-engine.

Number of segments

The maximum number of segments that can be modelled on your system depends on the ofphysical memory (RAM) available on your computer. For different number of segments separateengines (requiring different amounts of memory) are selected by 4nec2.

Select ‘Help -> About 4nec2’, to see the total amount of physical memory available on yoursystem.

In version 5.0 or later, 4nec2 automatically calculates the engine-‘size’ that is required. Mostly thiswill be fine. The engine selected is the one specified by both the number of segments (andpatches) in your model and the ‘Min-nr of segments’ setting (see below). If segment-count goesup, a ‘larger’ engine is automatically selected.

However in special cases when using the the NGF (numerical Green’s fuction) or related to GXand GM cards, it is possible the wrong engine is selected. (an error like: “nr of segments andsurface patches exceeds dimension limit” may be generated). If this is the case when using aNec-2 based engine, you could switch to ‘manual selection’. To do this, set the ‘Manual select’option and then specify the ‘Max-nr of segments’ setting. The engine(size) used now is selectedaccording the number of segments specified.When using a licensed Nec-4 engine you can use this option to manually specify the executable

file-name to use as the NEC-engine The following table gives you some indication about the available public-domain Nec2d engines,the maximum number of segments to calculate and the minimum required amount of RAM. Notehowever that these numbers are based on running the old DOS operating system. Because4nec2 is based on the windows-XX system, less memory is available for the nec engine,especially when running windows-XP which uses a large amount of available memory byitself……

Name of Max number Approximate executable of segm. memory use (MB) - - - - - - - - - - - - - - - - - - - - - - / NEC2D.EXE 256 1.5 (*) These are | NEC2D512.EXE 512 5 found in | NEC2D960.EXE 960 16 nec-pc.zip | NEC2D1K4.EXE 1392 32 \ NEC2D1K9.EXE 1950 60 / NEC2D2K8.EXE 2800 122These files | NEC2D4K.EXE 4000 247 are in | NEC2D5K7.EXE 5700 500nec-pc-x.zip| NEC2D8K1.EXE 8100 1006 \ NEC2D11K.EXE 11000 1852

(*) NEC2D.EXE should be in the directory from where you run the other executables, it is the only one that contains the DOS-extender. The others borrow it from NEC2D.EXE.

Nec2dXS engines are available for the following maximum number of segments:

Nec2dXS500 max 500 segments (5 Mb)Nec2dXS1k5 max 1500 segments (40 Mb)Nec2dXS3k0 max 3000 segments (150 Mb)Nec2dXS5k0 max 5000 segments (512 Mb)Nec2dXS8k0 max 8000 segments (appr 1Gb)Nec2dXS11k max 11000 segments(appr 2Gb)

By default 4nec2 uses the smallest executable available for the number of segments specified in the*.nec inputfile. However when using the original nec2d engine this may cause problems on systemswith 128 Mb of RAM or more.

When using a 'simple' nec input file with few segments in combination with a 'small' exe and with a‘large’ amount of RAM, a message "Program requires MS-DOS mode,...." might be displayed. If this isthe case, increase the number of segments in the ‘nr of segments’ setting, till the message no longerappears. On the other hand, don't set a far too big number of segments, because this will decreasecalculating performance.

For troubleshooting and additional information about engine selection, see: troubleshooting

ZIP files for the nec2d and the nec2dXS executables can be found at the “Unofficial NEC archives”:(See http://www.si-list.org/swindex2.html) or on the 4nec2 home-page athttp://www.qsl.net/4nec2/index.html. These *.exe files should all be placed in your ..\4nec2\exe folder.

Additional notes:

(1) The Nec2d engine used is the one created by Jos Bergervoet.(2) The Nec2dXS engine is based on the nec2dX engine made available by Raymond Anderson.(3) The Nec4D engines are available as a licensed product from Lawrence Livermore National Laboratory.

The Nec2dXS engine is an improved engine as it does not require the additional Somnec2d.exeprogram. Besides this, when running a Nec-2 frequency sweep the Real/SomNec ground data isrecalculated for every frequency-Step. The original nec2d engine calculates this Real/SomNec grounddata only once (using a negative conductivity setting. For more info, see nec-2 user-manual), soaccuracy is improved. #$K

ItsHF Propagation prediction using the ItsHF package

In this paragraph the Area- and Point-to-Point Coverage options available with the Generate commandare described in more detail. These both options are used in conjunction with the HFwin32 highfrequency propagation-modeling program developed by NTIA/ITS, which is freely available on theInternet. (See http://elberts.its.bldrdoc.gov/hf.html) or do a Google search.

Within the combination of 4nec2 and the ItsHF package/program it is possible to createArea-Coverage maps or create Point-to-Point plots. By default the ItsHF package contains a numberof pre-defined antenna types to be used for propagation prediction. 4nec2 however enables you tocreate your own ItsHF type antenna input files based on your (4)nec2 model.

On the Generate (F7) form you can choose between two 4nec2 specific types of ItsHF antennafiles to create:

- 360 degree Gain-table (Type 13: 360 degree Gain-table (Gain table versus azimuth and &elevation angle)

- Gain @ 30 frequencies (Type 14: Gain-table at 30 frequencies (Gain versus elevation angle &frequency)

When running a propagation prediction both Transmitter (Xmtr) and Receiver (Rcvr) antenna must bespecified. If <current> is set as the antenna (type) to use, the above selected antenna-type isautomatically created from your Nec model (if not already available) and used for the prediction.

Running a prediction

Before running a propagation prediction you must choose between four types of plots:

Map Area-coverage plot showing propagation performance on a (partial) world-map.

Time Point-to-point chart showing propagation performance as function of time-of-day

DistancePoint-to-point chart showing propagation performance as function of distance

Graph plot Point-to-point chart showing propagation performance as function of time andfrequency

After having selected the required plot-type additional settings can be specified and/or modified as listedbelow:

Phi-max

(or Azim-max) When generating an ItsHF antenna-file you will have to specify the NEC basedphi/azimuth angle for the main beam for the antenna under test. Usually this will be 0 or 90 degrees.This value is used so the NEC main-beam angle corresponds to the ItsHF main-beam azimuth angleof 0 degrees.

Bearing

For a point-to-point type of plot (time, distance or graph) it is required to specify both the transmitter

and receiver location. Both these locations determine the antenna direction (bearing) from transmitterto receiver and from receiver to transmitter. When changing one or both locations the antennadirection for the transmitter is automatically updated. Manual modification however is still possible. Foran area-coverage plot a receiver location is not strictly needed. This location however is used todetermine the default antenna direction.

Map

This box let’s you select between the different map ‘sizes’ for an Area-Coverage plot. Selection isdisabled when a time, distance or graph type plot is selected. When using <default> the setting asspecified in the 4nec2.ice (.rec or .voa) template file is used

Power

Using this text-box you can overrule the default transmitting power as specified under 'Settings on theMain (F2) window.

Param

This selection box let’s you select between the different parameters to visualize on the plot. Selection isdisabled for a ‘Graph’ type of plot. For the moment you can select the following:

- <use default file> Use parameter(s) as specified in 4nec2 template file (see below).- Signal at receiver SDBW – Monthly median signal power at receiver (dBW).- Noise at receiver NDBW - Monthly median noise power at receiver (dBW)- Field strength DBU – Monthly median field strength at receive location (dBu)- Signal/Noise ratio SNR – Monthly median signal-to-noise ratio (dB)- % above req. SNR REL - Time availability, % days/month SNR exceeds required SNR- Max usable frequency MUF - Maximum Usable Frequency – monthly median (MHz)- Radiation angle ANGLE – Radiation angle at Xmtr (degrees)

Note: Due to some strange inconsistancy between the ItsHF Time/Distance and Graph type of plots, withthe Graph type plot it is required to manually select the required plot once the prediction calculations aredone and the ItsHF plot-window pops-up. This manual intervention is not required for theArea-Coverage, Time and Distqance plots.

‘Required SNR’ is specified using the ‘Mode of operations’ available through the <More> button.

See DBW and dBuV conversion for conversion from DBW and dBuV to S-meter readings.

Fixed

To set Fixed contour scaling for Area-coverage-maps and Graph-plots and fixed Y-axis scaling for time-and distance-plots. When not set scaling is done automatically by the ItsHF program. FixedContour/Y-axis scaling is usefull when using the picture-viewer to scroll through a set of plot-files. Sets ofplot-files are created when a none-zero time-span is selected for area-coverage map’s or when the4nec2 Variable-sweeper is used.

You can use the ItsUtil.exe program (‘Run -> ItsHF colors and scaling’ on ‘Main [F2]’ ) to change Color-,Contour- and/or Y-axis-scaling for Area-coverage, Graph and Time/Distance plots to meet specificneeds.

Month

To select the (starting) month of interest. Furthermore this sets the so-called Smoothed Sunspot Number,

(SSN) which is an important propagation parameter. When selecting <def>, the value from the templatefile is used. If a certain month is selected, this value together with the specified year is used to let 4nec2automatically get the proper SSN from the internal ‘sunspot.txt’ file.

SSN

To select the year for setting the Smoothed Sunspot Number (see above) this selection box is used. Tomanually specify the SSN value (in the second text box), select the ‘manual’ setting.

UTC

The UTC selection box is used to specify the (starting) time-of-day for which a (set of) prediction(s)should be done. Set <def> to use the value from the template file.

Span

You can run multiple Area-Coverage or Point-to-Point Time, Distance or Graph plots for a selectedtime-span. When running an Area-Coverage predictions for a certain time-span, multiple plots are created. All plotsare automatically cut and pasted into the new ‘picture-viewer’ window with which you can manually scrollthrough or switch between the different plots.

When running a Point-to-Point Distance prediction for a certain time-span, you must use the ‘New plot’menu-bar option on the plot-window to manually select between the different plots. This same option isused to select between the different frequencies as specified using the <More> button (see below). Time,Distance and Graph plots are not automatically copied to the ‘picture-viewer’ window.

When an Area-Coverage map is selected additional ‘frequency’ and ‘month’ span-selections areavailable. These are used to create a set of plots for each frequency as specified using the <More>button or a set of plots for 6 months with 1 or 2 month interval.

Location

Both of these command buttons are used to specify the transmitter (Xmtr) or Receiver (Rcvr) location. Anew window will pop-up, in which you first will have to select the file-name containing a list of locations tochoose from. After this selection all locations in the file are listed on the second part of the window. Youcan click the top-row for a specific column of the list to sort the list. You can select a certain location bydouble clicking in the desired location.

Antenna

Using these both command buttons you can specify the antenna used at the transmitter (Xmtr) orReceiver (Rcvr) location. A new window will pop-up, in which you first will have to select the foldercontaining the antenna files to choose from. The 4nec2 folder contains the type-13 and -14 antenna-files created in previous 4nec2 sessions. Select<Current> to automatically create (or re-use) the type-13 or type-14 antenna-file for the current antennaunder test.After selection all antennas contained in the selected folder are listed on the second part of the window.You can click the top-row for a specific column of the list to sort the list. You can select a certain antennaby double clicking in the desired antenna.

The ‘Transmit’ and ‘ Receive’ folders contain general HAM related transmit- and receiving antennas. Allreceiving antennas are omni-directional and the Dipole- and Yagi-types are artificial derivations of theirdirectional counterparts.

These omni-directional receiving antennas are especially usefull for Area-coverage prediction, because

for each receiver in the ‘grid of receivers’ and as seen from the receiver another direction/bearingapplies. If you would use a directional receiving-antenna with a direction/bearing of 0 degrees (aimedNorth) the receivers North of the transmitter would be pointing with their backs towards the transmitterwhereas the receivers to the South would be properly aimed. If propagation would be the same in alldirections and you would use an omnidirectional transmitting antenna this would result in unequalcoverage.

These artificial receiving antennas are also perfectly usable as a receiving antenna in point-to-pointpredictions.

More (button)

This button is used to specify additional circuit related parameters:

Mode of operation which determines the minimum required signal to noise ratio for the selectedmode. (Used to calculate the ‘% above req. SNR’ (REL) parameter)

‘Noise level at receiver’, which specifies the Man-made noise level at the receiver location(s).

Above settings are used when running a ‘Signal/Noise ratio’ (SNR) or ‘% above req. SNR’ (REL)prediction

‘Extra Frequencies’, for the Point-to-Point Time- and Distance-plots, additional frequencies tocalculate a plot for can be specified. After prediction calculations are done you can use the ‘Newplot’ menu-bar option on the ItsHF time- or distance plot-windows to select a plot for a differentfrequency or even for all frequencies at once.

Using the ‘HAM-bands’ or ‘ Broadcast’ buttons, initial/default frequencies for Ham- or Broadcastbands are set. One can manually change these values.

When using the ItsHF package its important to keep in mind that the ItsHF programs uses azimuth andelevation angles whereas 4nec2 and NEC by default use Phi and Theta angles. For later 4nec2versions however it is possible to switch between Phi/Theta and Azimuth/Elevation presentation.

When elevation increases from 0 to 90 degrees, the theta angle changes from 90 or -90 degrees to 0degrees. Azimuth increases in a clockwise direction from 0 to 360 degrees. Phi increases in ananti-clockwise direction from 0 to 360 degrees.

All automatically generated area-coverage or point-to-point input-files are derived from default4nec2.ice, 4nec2.rec or 4nec2.voa template files as located in your ‘..\ItsHF\areadata\default’ or‘..\ItsHF\saved\default’ folders. This is especially true if, for the selection boxes on the Generate form,the <default> selection is used. When other selections are used the settings as specified in thetemplate files are overruled by the setting as selected. You are free to modify these template files. For instance to set a larger area-coverage grid-density.You can do so by using ‘Run -> ItsHF Area Coverage’ in the ‘Main (F2)’ window, select the ‘defaultfolder and open the 4nec2.* file. After modification, save this file under the same name. Next time yourun a predication the new settings are used (if not overruled by the user-settings on the Generateform). To use the ItsHF software package it must be installed on your computer system. Use 'Settings ->Folders' to specify your ItsHF home folder. In this same Settings-menu you can choose between theICEPAC, VOACAP or REC533 model to use for the propagation-prediction. At the time of writing this theVOACAP and ICEPAC models are considered to be the most accurate. Note that folder-namescontaining more than eight characters are not allowed. If possible use the default C:\ITSHFBC folder.

Propagation Prediction using the Variable-sweeper

You may use the Variable-sweeper to see the effect of changing certain antenna dimensions onpropagation performance. To do so, first select ‘ Sweep’ as the required function and then select‘type-13’ or ‘type-14’ as the antenna-type of interest using the ‘Option’ selection-box on theoptimizer/sweeper form. During sweep a number of ItsHF antenna-, input- and output/plot-files arecreated. For this, the 4nec2 (antenna) filename is truncated to six characters and a two charactersequence-number is added to this left-over filename to distinguish between the different calculationsteps. This may produce a lot of files in the ..\antenna\4nec2, ..\areadata\4nec2 or ..\saved\4nec2folders. If disk-space is an issue you may delete these files without further problems.

During the sweep all created plot-files are cut and pasted into the ‘picture-viewer’ window with whichyou can manually scroll through the different images if calculations and plottings are finished. You canuse the ‘Save’ or ‘Print’ buttons to save or print specific images. Use the ‘Sel(ect)’ button to select partof an image for save or print.

Steps to distinguish when running a prediction:

For Area-coverage map generation 4nec2 processes the following steps:

1) Nec is run and depending on the antenna-type selected, output data for a 90 * 360 sample far-fieldrequest or for a 90 sample far-field request at 30 frequencies is generated and translated into atype-13 or type-14 antenna input-file with name <name>.n13 or <name>.n14.

2) From the ItsHF parameters specified on the Generate form and (depending on the model selectedin the settings menu) a <name>.ice, <name>.rec or <name>.voa Area-Coverage input-file iscreated.

3) Using both the Area-coverage and Antenna input-files the ItsHF engine for the specified model isrun and an Area-coverage plot/output-file is created with name <name>.ig1, <name>.rg1 or<name>.vg1

4) If not specified otherwise in the settings menu the generated output/plot-file is displayed on thescreen. You can move the mouse around the Map and click a location to read distance andparameter values or use the ‘Parameter’ menu-option to select another parameter to plot.

For Point-to-point plots, 4nec2 processes the following steps:

95 Nec is run and depending on the antenna-type selected, output data for a 90 * 360 samplefar-field request or for a 90 sample far-field request at 30 frequencies is generated andtranslated into a type-13 or type-14 antenna input-file with name <name>.n13 or <name>.n14.

96 From the ItsHF parameters specified on the Generate form and depending on the modelselected in the Settings menu a <name>.ice, <name>.rec or <name>.voa Point-to-pointinput-file is created

3) Using both the Point-to-Point and Antenna input-files the ItsHF engine for the specified model isrun and an Time-, Distance or Graph- output-file is created with name <model>T.dat,<model>D.dat or <model>G.dat

4) If not specified otherwise in the Settings menu the generated output-data is displayed as a Time,Distance or Graph plot on the screen. You can manually select between the different time- and/orfrequency plots using the ‘New plot’ menu-option.

The following files/extensions are used in the process:

ICEPAC VOACAP REC533

- Type 13 ant-file: <name>.n13 <name>.n13 <name>.n13- Type 14 ant-file: <name>.n14 <name>.n14 <name>.n14- Template-file: 4nec2.ice 4nec2.voa 4nec2.rec- Area Input-file: <name>.ice <name>.voa <name>.rec- P-to-P Input-file: <name>.ice <name>.voa <name>.rec- Area output-file: <name>.ig1 <name>.vg1 <name>.rg1- P-to-P output-file icepacX.dat voacapX.dat rec533X.dat

For the P-to-P output file the ‘X’ character is replaced by T, D or G for Time, Distance and Graph plotrequests.

Type-13 and –14 antenna input-files are created in folder ‘..\ItsHF\antennas\4nec2’. Area-coverage input-files are created in folder ‘..\ItsHF\areadata\4nec2’.Area-coverage plot-files are created in folder ‘..\ItsHF\areadata\4nec2’. Point-to-point input-files are created in folder ‘..\ItsHF\saved\4nec2’. Point-to-point output-files are created in folder ‘..\ItsHF\run’.

The filename <name> for your antenna under test is truncated to eight characters for use with theItsHF software.

#$K

360 degree Gain-table

(Type 13: 360 degree Gain-table [Gain table versus azimuth and & elevation angle])

When using the ItsHF software to run a propagation prediction, one needs to specify theantenna-types used at the transmitter (Xmtr) and receiver (Rcvr) locations. ItsHF by itself alreadycontains a large number of more or less general antenna-types. Performance (radiation pattern) forthese pre-defined antenna types is determined by equations, which are run by the ItsHF engine whena prediction is done. You can view the far-field radiation patterrn for these predefined antennas by using the ItsHF built-inantenna-viewer. This viewer is started using the ‘Run -> ItsHF antenna-view’ menu-command on the‘Main (F2)’ window.

On the other side ItsHF enables us to use so called gain-tables, in which for each theta/phi valuecovering half the hemisfere a gain-value is listed. When propagation in a certain direction has to becalculated, ItsHF consults these tables and uses the listed gain for the required direction.

When using 4nec2 together with the ItsHF software we distinguish two different antenna-types usinggain-Tables: a) the type-13 antenna, containing a full 3D 90*360 degree gain-table for a single frequencyand b) the type-14 antenna, containing a set of 1*90 degree gain-tables for specifiedphi/azimuth-angle, but for all integer frequencies from 1 to 30 Mhz.

Both of these antenna-types are created using 4nec2. This is automatically done by selecting therequired antenna-type in the ‘Generate (F7)’ window. If an antenna-file for the selected type is alreadyavailable it is re-used. You can overrule this behavour by checking the ‘run Nec’ check-box.

The ‘360 degree Gain-table’ option on the Generate window lets you generate 360 * 90 degreeGain-table file for a single frequency (type-13). This type of file is the default antenna file to use forcalculating and plotting Area-coverage Maps for your antenna structure under test.

When running a Time- or Distance plot for the working/design frequency for the antenna under test (asis the case running a plot through 4nec2) a type-13 antenna files is the one to use. However whenTime/Distance plots for multiple frequencies are run, type-14 files are preferred.

When using a type-13 file to run a Area-coverage map for multiple frequencies or to create aPoint-to-point Graph type of plot (propagation versus time and frequency) keep in mind that this single360 degree radiation pattern is used for all frequencies steps ranging from 2 to 30 Mhz, so type-14antenna-files (Gain @30 frequencies) are the better choice.

#$K

Gain @ 30 frequencies

(Type 14: Gain-table at 30 frequencies [Gain table versus elevation angle & frequency])

In the description about the type-13 antenna-file it is explained how these antenna-files are createdand how these are used by 4nec2/ItsHF.

The ‘Gain @ 30 frequencies’ option on the Generate window lets you create a set of 1 * 90 degreegain tables for a single Phi/Azimuth angle. For each whole/integer frequency between 1 and 30 Mhz aset of 90 gain values (one for each theta/elevation angle) is generated.

The Phi/azimuth angle for which each vertical pattern is generated is defined by the differencebetween the real ‘bearing’ between the Transmitter- and Receiver location (listed behind the Xmtr/Rcvrantenna button) and the ‘Bearing’ (antenna direction) value as (manually) specified on the ‘Generate’form.

This type of file (type-14) is the default antenna input-file for calculating and plotting the point-to-pointGraph type of plots (frequency/time). These graphs for instance can show you the MUF, SNR or fieldstrength as function of frequency and time of day.

Type-14 files can also be used for multi-frequency Area-coverage and point-to-point Time- andDistance-plots. When a none integer (design) frequency is specified used/selected the pattern to beused for the prediction is interpolated from the patterns for the two nearby integer frequencies.

When generating a type-14 antenna file through 4nec2 note however that segmentation can becomean issue. because both at 2 and at 30 Mhz Nec-requirements must be met. Depending on thefrequency range of interest and the accuracy needed, you can run a default 4nec2 far-fiels 3D patternat both the upper- and lower frequencies to check if Nec-requirements are not violated or not, and ifso, how much.

On the other hand however one will rarely use a single antenna for all frequencies between 2 and 30Mhz. For those who would like to specify different antennas for specific frequency-bands or –rangesone could use the original ItsHF point-to-point user inteface. With this it is possible to specify up to 10different antennas with corresponding frequency-ranges.

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3D viewer form F9 Show geometry/pattern in real-time 3D.

The 3D-viewer form is available only for the extended freeware version 4nec2X, and requires acomputer system on which the Microsoft DirectX 8.0 or later hardware–acceleration drivers areinstalled. For further information about how to check for DirectX or how to install, see the_ReadMeFirst.txt file.

The 3D viewer is used to display structure geometry and/or 3D far- and near-field pattern in real-time3D. Compared with the Geometry-view F3, this viewer shows the structure much more as it is inreal-life. It also shows the real wire-radius. However when the radius becomes too small to be visible, for instance for wire-antennas, a correctionis applied on the wire-radius, to keep it visible. A check box is available on the right of the form, whichis enabled if it’s possible to re-enable the real-radius display. This way it is very easy to see if wires are overlaid or intersect (at unexpected places) or not. Also atjunctions with short fat segments the intersected area should not be more than about 1/3 of thesegment length. With some experience it’s also possible, for wire grids, to check the ‘equal area’ rule.

When patches are included in the structure geometry, the ‘shiny’ side of the patch is the one fromwhere the normal-vector is pointing outwards. This side of the patch should be considered as beingpart of the NEC calculation process.

Use the structure drop-down box to select different structure-display options.Use the ‘Res’ button to reset all zoom-, shift- and/or rotate-actions.

The following key’s and mouse-buttons are available to change the viewing-position.

Key-combination: Mouse-action:

- Rotate structure Left/Right or Up/Down arrow Move mouse with left button pressed- Move structure Ctrl+Left/Right-arrow Move mouse with right button pressed- Forward/backward Ctrl+Page-up/down Move mouse with both button pressed- Zoom-in/out Page-up/down

When the display of currents is enabled, and also a freq-sweep calculation was performed, thefunction of the cursor/arrow key’s is changed from structure movement/rotation to frequency‘movement’.

The upper drop-down box lets you select different types of structure (geometry) display. If ‘wires’ or‘segments’ is selected, the red end is end-1 and the green end is end-2. If ‘currents’ is enabled use the ‘Log factor’ scroll-bar to visualize small currents on gridded/externalobjects.

If NEC output-data is available the drop-down boxes on the right of the form are enabled. This letsyou visualize the 3D far- or near field E/H pattern in 3D. You have the choise between single-color ormulti-color mode. In multi-color mode a blue to red scale is applied to the pattern for which the colorcorresponds to the color-scale on the left of the form.

When, for the far-field, the 2D-slice display option is selected, a 2D-pattern slice is displayed for acertain theta/elevation or phi/azimuth value. You can change the Theta/Elevation or Phi/Azimuthangle for which the slice is displayed, on the ‘Pattern (F4)’ form while simultaneously watching the 3Dform. In the ‘Pattern (F4)’ form, use the space-bar to switch between horizontal/vertical slice.

When on the Pattern-form multiple far-field patterns are selected to be compared against each other,

you can also switch between these patterns on the 3D-viewer form. Use the selection-box in whichthe file-name is displayed to select one of the patterns. You may also use the ‘<’ and ‘>’ keys (with orwithout <Shift>)

On certain computer monitors it showed up that color display sometimes is not optimal. To overcomethis ‘problem’, use Ctrl+C to bring-up the color settings window. Select the appropriate structure partand use the sliders to change color or to alter background- or, directional-light intensity.

When no key’s are pressed for a certain amount af time, the structure is rotated automatically. Youmay maximize the window and use this functionallity as a kind of screen-saver. You may use the ‘Z’key to start to spinning directly without waiting for the time-out.

When structures are viewed with a large number of (bent)segments and/or junctions, a certainsimplification is done when creating the 3D picture. For instance, by default, all wire ends are closedand wire-radius-changes and junctions for more than two segments are smoothened.

For very high-segment structures these actions are not performed. This is represented by the ‘Quality’slide bar on the lower right corner. Eventually one can use this slide-bar to change the default 3Dstructure quality and increase speed, ranging in three steps from left to right.

- Left : Show ‘simple’ structure as a wire-grid.- Middle : Show structure with open ends and none smoothed junctions- Right : Show high-res structure with closed ends and smoothed junctions

FPS = number of frames (screen refreshes) per second.Tri’s = number of triangles used to constuct the 3D objects

When a large number of far/near-field points is requested or when structures with a large number ofsegments and with ‘high-quality’ are viewed, it could be necessarry to increase the ‘Max-nr of3D-points’ in the setting-menu. If so, a message will inform you about this possibility. However,because this setting also affects the amount of video-card memory used, large values cansometimes result in strange video effects. If so, lower this setting.

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Matching F10 Impedance matching networks.

For maximum power transfer from the source to your antenna/load and/or to reducetransmission-line losses it is needed to match your antenna to the characteristic impedance (Z0)of your feed/transmission-line. In many cases however it is not possible to choose all impedancesuch that overall matched conditions result. These situations require that matching networks beused.

In general, matching networks are constructed with reactive components only so that minimalloss is added to the overall network. For frequencies up to approximately 500 MHz matchingnetworks containing lumped elements (L, Pi or T networks) may be used. The circuit elements(capacitors and inductors) must be small enough relative to wavelength.

Another way of antenna to feedline matching is called Stub-Matching and uses parallel or seriesstubs. These stubs are open or closed (at the end) pieces of transmission-line with differentimpedance placed somewhere along the feedline. A third method is called Series-Matching. This method uses a series matching system consistingof three sections of transmission line. The middle section does have different characteristicimpedance.

L, Pi or T-network matching

Using L, Pi or T-networks it is theoretically possible to match any source/load impedancecombination. However in practice certain reactance/resistance values could result in additionalcomponent losses and the use of lumped elements does reduce your overall system bandwidth.

4nec2 supports the automatic calculation of the required components for low- and high-pass L, Piand T(ee) networks using the ‘Matching (F10)’ window/form.

When this form is first displayed 4nec2 checks if already a matching network is present. If not, theantenna/structure input-impedance value and the design-frequency is copied into the ‘Matching(F10)’ form and the Z0 as specified under the ‘Settings’ menu is set as the (source) impedance tomatch. With these impedance’s then the required component-values to create low- and high-passL, Pi and Tee networks are calculated and displayed on the screen.

For both inductors and capacitors their quality ‘Q’ may be specified using the Q-coil and Q-cap.Text-boxes. By default capacitors are considered lossles (indefinitely high Q, entered as zero),whereas inductors are given a default Q of 250. If sufficiently high (100-300) then the low seriesresistance will not influence the required network components for a 1:1 match much.

To let 4nec2 automatically add the matching network to your (4)nec2 antenna design, first selectthe required network and then click the “use network” button and let 4nec2 generate new NECdata. You can use the default option “use original file” to generate only the new input-impedance.

If done so, 4nec2 will create a (far-away) dummy wire, place the voltage-source on it and connectthis dummy wire with the original excitation wire/segment through a network NT-card. The Y11,Y12 and Y22 values to be used with the NT card are calculated when the network is selected.After generation the new input impedance together with the resulting losses for the selectedmatching network will be displayed on the ‘Main (F2)’ window.

As long as the ‘Matching (F10)’ window is active you can re-generate using other selectednetworks. Once the ‘Matching’ window is closed you will first have to generate the ‘raw’

input-impedance using the default ‘Generate (F7)’ function, before you are able to use the‘Matching (F10)’ window again.

For Pi and Tee networks by default 4nec2 uses the lowest possible Q. This to minimize losses. Ifmore manageable components or extra attenuation of undesired frequencies is desired (for Piand Tee) a different/higher value may be specified in the min-network-Q textbox. A highernetwork-Q however will increase network-losses and reduce bandwidth.

Note:

- You may manually change Z-ant, Z-src and/or Frequency to let 4nec2 directly reflect thesechanges in the calculated L, Pi or Tee network-values. This way you can use this form as ageneral tool to match for other impedances and/or frequencies- After a certain L, Pi or Tee network has been selected, you can also manually changecomponent values (L, C, Ql or Qc) or the network-Q to see how these changes directly affect theNT network parameters Y11 to Y22.- Click the ‘use network’ button to see the effect on overall input-impedance and power losses inthe network due to your manual changes (tolerances) of Network component values.

You will see that using inferior components and thus lowering component-Q (and increasingnetwork-Q for Pi/Tee) will increase losses and deviate the input-impedance more and more fromthe specified Z0. On the other hand an infinite high coil- and capacitor-Q (enter a value of zero)will deliver an exact 1:1 match.

Click the <Reset> button to restore all fields to their initial values.

Stub/series matching

You can reach the stub/series matching form by clicking the ‘stub’ button on the upper-right on theNetwork matching form.

When the form is first displayed 4nec2 checks if a matching network is already included. If not,the antenna/structure input-impedance value is copied onto the Stub-matching form as ‘Z-load(antenna). The design-frequency and the Z0 (as specified on the Main-form’s settings-menu) arealso copied onto this form.

With the ‘select matching network’ selection box you can choose between the matching networkto use. For now, below types are available:

- Series section; this type of match uses three sections of transmission line in series, in which themiddle transmission line does have different impedance. The impedance transformation isdefined by the Z0 of the series section, the length of (default) feed/transmission-line from antennato the middle series-section and the length of this series-section. An arbitrary third (lower) lengthof (default) feed-line connects the series section to your rig.

- Parallel stub, open or short; this type of matching-network also uses a second different type oftransmission-line which is connected somewhere between the antenna and your rig on thefeedline. The parallel stub is connected as the name already implies in parallel with your feedline.The impedance transformation is defined by the distance between antenna and the point on thefeedline where the stub is connected and the characteristic impedance and length of thestub-line. The required lengths are influenced by the fact weather you choose to use a short oropen end for you stub.

- Series stub, open or short; this matching-network uses the same principles as the parallel stub,but now the stub is connected in series with one of both feeder-lines. For the series stub one canalso choose between an open or a short stub. Also included on the form are two selection boxes to select both types of feed/transmission-line.The first sets your default type of feedline; the second sets the characteristics for theseries-section or stub-line. When ‘user-specified’ is selected you can manually entercharacteristic-impedance (Z0) and/or velocity-factor (Vf) values.

For each selection the resulting line-length results are displayed in the lower ‘edit/select results’portion of the window. If ‘none’ is displayed, there is no valid solution for the selected networkand/or type of transmission-line(s). You will have to select another network or transmission-line.For each selection 2 possible solutions are available, labeled A and B. When stub-matching isused one can furthermore select between using a short or open stub. This selection is done byusing the ‘select solution’ selection-box or by clicking on one of the length text-boxes. Valueshighlighted represent the actual selection.

To use the selected matching-network with specified lengths in your model, click the ‘useselection’ button. 4nec2 will now automatically add the required transmission lines to your modelwith the specified lengths and configuration and calculate the results, which are displayed on theMain(F2) and Geometry(F3) form.

You can also manually overwrite the lengths as initially calculated by 4nec2 on the stub-matchingform. This way you are able to see what results you get if you do not exactly follow the calculatedline-lengths.

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Smith Chart F11 Show impedance and SWR on Smith-chart

In this form the input impedance is plotted on a Smith-chart. When a Nec based frequency-sweep wasdone more than one impedance point is plotted. The active SWR is displayed as a circle. On the left ofthe Form additional information such as reflection loss, SWR in dB, refl-coeff (U/I), refl-coeff (P) andreturn loss is displayed.

With the Shit+left or Shift+Right buttons you can specify any length of transmission line connectedbetween the load and the generator and read the resulting impedance. With Ctrl+P you can captureand save/print the Smith-chart form for further graphical analysis.

When you requested a frequency-sweep you can 'walk' through each frequency with the RIGHT andLEFT arrow-keys. The corresponding frequency and the real and imaginary values for the impedanceare displayed in the lower right of the form. With the 'X' button you can switch between polar- orcartesian-notation. With the 'Home' button you can switch between a normalized chart or a chartbased on the characteristic impedance.

With pressing the Right or Left button together with the SHIFT button a second phase line is displayed.With this line you may specify a length of feed-line. On the lower left of the form a second pair ofvalues is displayed, showing the real and imaginary values for the impedance on the other side of thisfeed-line, corresponding with the given SWR and phase angle.

When selecting a phase difference of 180 degrees (lambda/4) this can also be used for reading theadmittance values for the selected impedance. You can add and remove your own userimpedance/admittance points by pressing the Insert and Delete keys.

The grid for the Smith chart can be changed between fine and course with the corresponding optionunder the Show menu-bar option. For those who want to further customize their grid layout; the layoutis described in the Smith.dat files in the “\exe” folder, but before changing it, be sure you made abackup or this file.

Position your mouse and push <Insert> to add manual points, or use right mouse-button. Push<Delete> to remove last manual point.

Use the ‘Export’ menu-bar option to export your smith-chart data in Touchstone (Z or S params) orMicrosmith (*.gam) format. Use the ‘Import’ menu-bar option to (re)import a Touchstone (Z or S prams) or Microsmith (*.gam)data/export-file. When importing data you are asked if existing data-points should be cleared ot not. Ifexisting data is cleared, the new import data is also available through the line-chart form.

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The Optimizer and sweeper F12

The optimizer/sweeper is started by pressing the F12 key or by selecting calculate -> optimize on themenu-bar in the Main window. The optimizer, as part of the 5.4 and later versions, contains fourdifferent options:

- Optimize Use the traditional hill-climbing method to optimize you design- Evolve Use Genetic Algorithms to evolve (optimize) your antenna design - Sweep Use the Sweeper to visualize the effect of user specified design/variable changes.- Conv-test To validate your model by running an automatic Convergence-test

You may select between one of these options with the "Function" box on the upper-left of the optimizerwindow. With the "Option" box you can select between different sub-options. For most cases 'Default'will be the appropriate choise.

The traditional hill-climbing optimizer was based on principles as described by Brian Beezley and usedby the AO (antenna-optimizer) program. A scaled down freeware version of this program is available atthe ARRL web-site.

For a description of how to ‘evolve’ your desing using the genetic algorithm based optimizer seeGenetic Optimizer, but before doing so, please read the below section about how to specify theantenna properties and variables to optimize/evolve. A description of the traditional hill-climbing optimizer is given below, a description of the Sweeperfunction is given in a separate section. How to run a convergence-test is described in Conv-test.

When you want to use the optimizer the 4nec2 input file must include variables (constants). Thesevariables serve as input for the optimizer. You may specify any combination of variables (and/orequations) anywhere in your 4nec2 input file (GW, LD, EX, FR card).You can select only “simple” variables (constants) as the ones to optimize. These are variables notcontaining any expressions like +, -, *, functions and/or other equations. These "simple" variables arethe ones that are altered during the optimization process. (See the 3el-inverted-V.nec file for a morededicated example).

The optimizer window is devided into four different sections, one input and three output sections.

Antenna properties to optimize

The main input-section is named 'settings', and is used to specify the variable(s) to modify and the(antenna) properties to optimize. These properties are SWR (standing wave ratio) ,Gain (forward gainor Electric-fld), F/B (Front to back ration), F/R (Front to Rear ratio), R-a (Input resistance), X-a (inputreactance) and/or Eff. (Efficiency). When the 'include surface wave' box is checked, the Gain propertydefaults to E-fld.

For each of these properties you must specify the importance of it by specifying a value between 0 and100% (weighting factor). This factor determines the effect on the overall performance for thecorresponding property. For instance when optimizing only on SWR, the SWR factor is 100% and theother factors are set to zero. You can toggle this weighting factor between 0 and 100 by right clickingon the "SWR", "Gain", "F/B", "F/R", "R-a", "X-a" or "Eff." text label or on the corresponding text box.Other values have to be entered by keyboard. (Negative values or values > 100% are allowed).

By default the SWR and X-in properties are minimized and the Gain, F/B, F/R, R-in and Eff. propertiesare maximized. In order to change these defaults or to specify your own targer value, click with theright mouse-button on the corresponding text-label (SWR to Eff). A pop-up menu is displayed in whichyou can specify if you want to maximize or minimize this property or if you want it to reach a

user-specified target value.

The following targets are set when optimization towards minimum or maximum (the default) isselected:

Property Min Max

SWR 1 100Gain -999 100F/B -999 +999F/R -999 +999R-a 0 9999X-a 0 +9999Eff. 0 100

When no (wire)loading cards (LD) are included, optimizing on efficiency has no effect.

User specified targets are accepted for values anywhere between -9999 and +9999. Note howeverthat if one specifies a target of +9999 for, for instance, forward Gain, this does not improve optimizeraccuracy. A target in or near the range of theoretical (min/max) property values for the antenna type tooptimize will yield better results.

The absolute difference between the actual value and the target value for each property is rescaled toa range from 0 to 10000 and summed according the specified weighting factors. The resulting value isused as input for the optimization process.

The optimizer calculates electric-field values in relation to the specified input power value, sooptimization is done with a constant power setting and not as might be expected with a constantvoltage (or current) setting. If the latter is required, select a power-level of zero watts and specify anappropriate voltage- or current-source.

When optimizing for (forward) Gain or F/B-ratio you will have to specify the Theta and Phi angle forwhich the Gain (and F/B, F/R ratio) should be calculated. If a resolution of 0 degrees is specified theGain (and F/B ratio) is calculated for this one and only angle. To optimize on F/R-ratio it is required touse a none-zero resolution to enable gain calculation and maximization to be performed for the whole180 degree backward-region.

It is possible to specify a certain forward- and/or backward-region for which the Gain or F/B ratioshould be averaged. This is done by specifying a certain resolution in combination with a delta-Phiand/or delta-Theta (d-Phi, d-Theta) value. Averaging is performed for angles between Phi – d_Phi andPhi + d_Phi. The same holds for the Theta and d_Theta angles. The resolution determines how manyiteration-steps are made between + d_Theta/Phi and – d_Theta/Phi angles. Using a none-zeroresolution will show a considerable increase in required optimization time, because far more gainangles are calculated.

Frequency-sweep

With version 5.1 the possibility to optimize over a certain frequency-band (for instance the 40-meterband) was added. To enable this option, check the ‘freq-sweep’ box. If done so additional input-boxesare displayed in which you can specify the start- and stop-frequencies and the step-size thusspecifying the frequency-band of interest.For each frequency step a complete set of results is calculated. All results for each property are thensummed and devided by the freq-step count at the end of the sweep to get the average values to beused as input for the optimization process.

Antenna dimensions/characteristics to change

To optimized one or more of the properties, antenna dimensions/characteristics have to be modified.These dimensions/characteristics are represented by (combinations of) “simple” variables. All available“simple” variables to optimize are displayed in the upper left box on the settings section. You selectone or more variables by clicking on the variable name. Then this variable is added to the box on theright. This box lists all the variables, which are used to optimize the selected antenna properties. Youcan remove a variable by clicking again on the variable name in the left or right box.

When using the genetic optimizer (evolve) you will also have to specify the minimum and maximumallowable variable values. This determines the so called 'search-space', in which feasible solutions aresearched. By default the minimim value equals the actual variable value devided by 2, the maximumvalue equals the actual value times two.

The traditional optimization process

If the traditional optimizing function is selected, clicking the 'Start' button starts the optimizer. First of allsome initial calculations are done to determine the sensitive and direction for the selected variables onthe requested propertie(s) to optimize. The results of these calculations are shown in the upper rightsection. After that, the actual optimization is started and the variables are modified with a certain initialstep-size to achieve better performance. The results of these optimization steps are displayed in thelower left and right section.

The first initial/max step size determines how quickly an optimization solution will be found. A smallstep size could lead to a long optimization run. With a too big step size it is possible that with sensitivevariables it is possible that the first minimum/maximum is skipped. This value is available in the'Settings -> optimizer' menu. Mostly a max/initial step size of 10% will be fine.

Optimization steps continue as long as there is still improvement. When there is no furtherimprovement a new sensitive run is performed to determine how the selected variables have to bemodified to achieve, if possible, a new better performance and new optimization steps, with smallerstep sizes, are done. This continues till the step-size has reached a certain minimum step-size and theoptimization process stops. This minimum step size determines how accurate the minimum/maximumwill be. This value can be changed in the ‘Settings -> Optimizer' menu. Mostly a value of 0.01% will befine.

By default the delta step size is relative to the active value of the variable to optimize. However it ispossible to use absolute (fixed) step sizes. If this option is selected in the Settings -> Optimizer menu,after a sensitivity run, an absolute delta step size is initially calculated and this step size value is notchanged until the minimum/maximum is passed and a new sensitivity run is performed.

You can examine the optimization results on the two lower output sections on the window.(Intermediate) variable results are stored in the file *.opt on the 4nec2 main home-folder.

To save the new optimized variable values to the original *.nec input file, use the 'Update Nec-file'button on the optimizer window. The existing variable values are overwritten with the new values.

It is possible to halt the optimizer before the process automatically stops by pressing the 'Halt' button.After the optimizer is stopped or halted you may exit the optimizer or alter, add or remove variable orproperty settings and continue by pressing the "Resume" button. The optimization process continueswith the latest calculated variable values. To (re)start with the initial variable values, you have to exitthe optimizer and start it again without saving the results.

When only one variable is selected the optimizer can be initially forced in a certain direction to find thenext maximum/minimum. This is done by selecting "increase" or "decrease" in the Upper left Functionbox on the 'Settings" section of the window. After the first maximum/minimum is passed, the normaloptimization process is continued.

After optimization it is wise to validate the new geometry structure, and if you updated/saved yourresults, to perform an additional Average-Gain-Test.

Additional Gain and F/B settings

When selecting Forward gain (Gain), front-to-back (F/B) or front-to-rear ratio (F/R) also the angleswhich define the forward- or backward-direction and a certain pattern-resolution must be specified.Optionally delta-Theta and delta-Phi values can be specified. This is used to average the forward(and/or backward) gain over a certain region between Theta/Phi - delta_theta/phi and Theta/Phi +delta_theta/phi. The step-size determines the number of averaging steps. (see Generate for additionalinformation. These delta-theta or –phi values can be used to minimize both maximum or averageside-lobe level in a certain direction.

By default when ground is specified, the backward theta/levation angle used for the F/B ratiocalculations is set to the same value as the theta angle used for the forward-gain (Theta-back =Theta-forward and Phi back = Phi-forward+180). If free space is selected the backward-angle used isthe angle on the opposite side of the XY plane (Theta-back = 180-Theta-forward and Phi-back =Phi-forward+180) It is possible to manually overrule the default backward Theta and/or Phi angles tobe used for the F/B ratio calculations.

Furthermore one may include ground wave calculations or select between Horizontal-, Vertical- ortotal-gain, E-theta, E-Phi or E-radial when performing the Forward gain of front-to-back/rearoptimizations.

Output log

During the optimization process, the optimizer variable- and property values (calculated results) arelogged in a log file called "Optimizer.log". This log-file is located in the 4nec2 home-folder. This log-fileis available for further examination of the results using the ‘Show’ command button. The next time theoptimizer is started, the old log-file is replaced with the new version.

To visualize the results and/or behavour of the optimization process one can use the ‘Plot results’command-button. After this you will be asked for a property- and one or two variable-names for whicha 2D or 3D plot is generated using the gnuplot program.

Tip(s):

1) During the optimization process you can resize or move the ‘Optimizer’ window to make more/otherdata visible. You can 'click' on one of the other windows or use the F2 to F5 key's to bring one or moreof the windows in front of the other or you can 'drag' one or more of the windows aside.2) You can only change a certain viewpoint on the 'geometry (F3) or 3D (F9) form or select a specific2D pattern type on the F4 form, when the optimizer is halted. You can do this before the 'Start' buttonis used, or you can temporarely pause the optimization after it is started by pressing the 'Halt' button,change setting and press 'Restart'.3) To sequentially switch from Genetic- to Hill-climbing-optimization or back, for the same input-file,use “Update Nec-file” to temporarely save the results of the previous run, exit the optimizer andopen/load this temporary file as input for the next optimization run. Use ‘seed with curr-data’ to useexisting optimization data in the Genetic optimization process.

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The variable-sweeper

In the optimizer window it is possible to evaluate the effect of changing one or more antenna orenvironmental dimensions. This is done by selecting the ‘Sweeper’ option in the Function box on theupper left of the Optimizer window. The dimensions to sweep must be specified as variables in the4nec2 input file.

After the Sweeper function is selected, one ore more variables to sweep have to be selected in the‘Available variables’ box. For each variable selected it is now possible to specify the min(start) andmax(end) values for the sweep. It’s not required for ‘max’ to be greater than ‘min’. For instance tosweep from 20 to 10 specify 20 as the ‘min’-value and 10 as the ‘max’-value.

Furthermore the number of steps for the sweep must be specified. This is done in the ‘Nr of steps’Box’. By default the ‘used fixed stepsize’ box is checked, resulting in equal steps when the variable valuesare changed from min to max. If un-checked multiplicative steps are used. In this case it is notpossible to sweep from <0 to >0 or reverse.

The Theta/Elev and Phi/Azim value boxes are used to specify the angles for which the forward gain,F/B-ratio and for none-zero resolutions, the F/R-ratio is calculated. It is furthermore possible to includeground wave data at a specified distance or to select between Horizontal, Vertical and total gain,E-theta, E-Phi or E-radial when sweeping on forward-gain.

If a none zero resolution is specified one can select between the horizontal or vertical (or 3D) patternto be displayed for each step during the sweep. The angle for which the hor/ver pattern is calculated isdetermined by the specified leftmost Theta/Phi values. All generated patterns can be played-back(using the arrow-keys) after the sweep when the Pattern form (F4) is selected.

Because full F/R (and F/B) data is not available when only far-field values are calculated for a certainhorizontal or vertical slice, the 3D-pattern option is available. Using this option full gain, F/B and F/Rdata is generated to be visualized through the ‘Line-chart (F5)’ window. When this 3D option isselected no horizontal or vertical far-field pattern play-back data is available, because only the lastgenerated full 3D pattern is stored.

Sweep output data (to be imported in a spreadsheet or other programs) is also reported through theoptimizer/sweeper logfile. To view this data, select ‘View -> Optimizer log’ on the Geometry window.

When a none zero resolution is specified, sweeping speed will decrease because of the additionalgain calculations, especially when the 3D option is used.

Note:

Sweeper results are stored in memory only and not on disk (as is the default 4nec2 behavour), so if4nec2 is shut-down or another (4)nec2 input-files is selected the sweeper results are lost. The log-fileis kept till a new optimization or variable-sweep is done.

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Convergence-Test

During a convergence test the design/model is validated by running it over a number of steps, in whichfor each next step the number of segments for all wire is increased by a certain amount (20-50%)while Gain, Input-impedance, Efficiency and other values are observed. These values will have toconverge towards a certain value.

To automatically run such a test select the Conv-Test function on the Optimizer window. If done so, thenumber of steps to run from default- to the highest allowable number of segments is calculated anddisplayed in the ‘Nr of steps’ text-box. When started, on each step the number of segment for wires(for which the highest allowable segmentation is not yet reached) is increased with 33%, till all wireshave (almost) reached maximum segmentation. When done, click the “Exit” button, and on the “Line-chart (F5)” window Gain- and Impedance-data isvisualized for further evaluation. Abrupt changes or an increasing slope for one or more of the graphson the chart could point to an unrealiable model.

For a description about how to use the Theta/Elev and Phi/Azim input boxes (to specify the angles forwhich Gaind and F/B ratio are calculated) see the Sweeper function.

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The Genetic Optimizer

The genetic algorithm (GA) used in 4nec2 is a real-value based algorithm. This GA includes anumber of selection-, crossover- and mutation-techniques like Roulette-Wheel-, SUS-, ortournament selection, N-point-, Blend- or Simulated binary crossover and random-, gaussian- ornone-uniform mutation.

Why use GA’s ?

GA’s are fundamentally different from other optimization techniques. Analytical optimizers usuallycompute derivatives (hill-climbing/gradient methods) to locate maximum or minimum points for thefunction being optimized. GA’s by contrast, create random populations of individuals/chromosomeswhich are then ‘evolved’ to converge to an optimum solution. Gradient methods produce one ‘best’answer, but they are often trapped in local extremes, which prevent the global optimum from beingfound. GA’s can produce groups of solutions, no one if which is necessarily the global optimum, but allof which are ‘good’ solutions.

Furthermore when a large number of variables is involved with mutual influences among each other,performance of the GA is expected to better than that of the Hill-Climbing optimizer. One drawback of GA’s is that it mostly takes more time to optimize a design using a GA than it takesto optimize using traditional methods.

Before starting the algorithm, the variables to optimize must be selected, together with theirminimum and maximum allowable values (limits). These user-selectable upper- and lower- limitsdefine the boundaries for the ‘search-space’. Mostly these limits are set according physical limits,like available space, maximum height or width etc.However, setting a too wide range may slow down the GA and might cause it to miss a goodsolution, because it searched not long enough. Setting a too narrow range might exclude useful andinteresting solutions. Experience in this is the most important factor and insight in what may affectantenna performance is also very usefull.

Each variable to optimize is called a gene. All the genes together form the chromosome. When theGA is started an initial random population is created by uniform random selection of the gene valueon the interval between the lower and upper variable limits.

A population is a group of N chromosomes or individuals. Each individual representing a different4nec2 antenna design. The GA ‘evolves’ the initial random population by creating successivegenerations of individuals. The population size N is constant from generation to generation, but theindividuals comprising the population are genetically altered from one generation to the other.

One of the most important features of a GA is its ability to optimize a population using any desiredmeasure of ‘goodness’. Unlike gradient methods GA’s easily handle discontinuous functions. Theonly requirement for a useful ‘Figure Of Merit’ (FOM) is that it is calculable. The data used for theFOM is usually generated by a separate computer program (calculation engine) that models thesystem being optimized and not by the GA itself. The GA inputs data from the engine and uses thisto computer the FOM or fitness values. This procedure is also known as the ‘objective’ function.

The FOM calculation used with the GA is the same as the one used with the traditional hill-climbing4nec2 optimizer.For one or more antenna properties a weighting factor from 0 to 100 (or more) percent is specifiedby the user, together with an optional target value (click on property using right mouse-button). Theabsolute difference between the actual value and the target value for each property is then rescaledto a range from 0 to 10000 and summed according the specified weighting factors. The resultingvalue is then used as input for the rank-based fitness calculations as described below.

Generation after generation is created this way with the expectation that each successivegeneration will contain better antenna designs. But because of its stochastic nature a GA may notcreate improved designs in every successive generation, and the FOM/fitness-value may actuallygo down. Experience has demonstrated that a well-designed GA will converge to an optimumsolution if allowed to run for enough generations with a sufficient large population size.

GA parameters

All parameters used by the 4nec2 GA are available on the ‘Optimizer’ form (F12). It may berequired to click the ‘GA’ (option) button to make them visible.

Max-generation.

This parameter sets the maximum number of generation after which the evolution of newpopulations will stop. You are now able to save any of the resultant antenna design files or exitthe optimizer and/or consult the summary log-file for all population data (use 'Show Log' button).You can also resume the generation of new populations by pressing the 'Resume' button. A newset of ‘max-generation’ populations is now processed.

You may halt Evolution, before the max number of generations is reached. For instance becausethe solutions have converged, an adequate solution is available or if you want to change one ormore of the Genetic Operators and resume.

Halt if N % same fitness

During the GA evolution process, the overall fitness of all the individuals will increase and finallyconverge around a certain solution. At this point most of the chromosomes (with exception of theonces just mutated) will have a similar fitness. You can specify to halt the optimization if a certainpercentage of individuals have reached the same maximum fitness value. Mostly this value willbe somewhere around 50-90%. To be sure all generations as specified by the ‘max-generation’setting are evolved, set this percentage to 100%.

Population size

This parameter specifies the number of chromosomes (individual antenna designs) included ineach population. As a general rule, values in the range 30-200 provide a good starting point,depending on the number of segments and how fast a CPU is available.

Seed with current data

This option is used to seed the coming GA run, thereby initiating the GA search around aparticular solution in its search space. The ‘seed’ individual (design) is inserted as individual #1 ingeneration #1. Its function is similar to the ‘Elitism’ function as described below.

Save best file for last N generations

When a GA run is completed either because it was aborted or because the maximum number ofgenerations was reached, all individual *.nec antenna designs for the last population are availablein the “\opt” sub-folder below your current *.nec input-file folder. Furthermore for a specifiednumber of last generations the *.nec file for the best individual is saved. This number of lastgeneration is specified in the field “save best file for last .N. generations”.

Update Nec-file button

This command button is used to let the user select the best file from last N generations. After thisthe original *.nec input file is updated with the new variable-values from the selected file and theresults are saved to a file with the same or a different name. This file could then be used as atemporary or final result or as a seed for subsequent GA runs.

GA specific parameters

The other GA specific parameters are described in the more general Genetic Algorithms section.These parameters are supplied for those who want to further explore the (dis)advantages ofGenetic Algorithms for optimization of antenna designs.

It is strongly recommended that every one using the GA optimizer reads this section.

As a good starting point one could use the below settings:

- Linear Ranking- Roulette Wheel Selection, chromosomes to re-use=1- Blend Crossover, alpha = 0.5, probability = 70%- Uniform mutation, probability = 4%

With all possible ranking-, selection-, crossover- or mutation-operators you will be able to get goodresults. However specification of very different crossover- or mutation probabilities may result inunsuccesfull or unwanted evolution of your design.

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Capture and Save or Print form/window (picture viewer)

With version 5.4.1 or later you can capture any form, window or other part of the screen for printing orsaving as a bitmap file. You can also copy the captured part of the screen to the clipboard to paste itinto your favorite text- or graphic processing tool. As an extra feature you can also paste any otherimage placed on the clipboard back into the 4nec2 capturing tool for printing or saving.

With version 5.6, additional functionallity (picture viewer) was added to capture a range ofpictures/images. Each additional picture pasted from the clipboard is added to the already existingrange of pictures/images. If two or more pictures are pasted, a scroll-bar is visualized with which youcan scroll through the range of pictures. You can also use the right- and left-arrow key for this. The ‘0’to ‘9’ number-keys are available for direct switching between two separate pictures. Thispicture-viewer function is used in conjunction with the ItsHF propagation prediction software to‘animate’ the propagation-changes during the day, the year, between different frequencies or as theresult of a antenna-variable sweep. To capture and print/save the current/active 4nec2 form, use the “Show -> Print” menu-bar option oneach form or use the Ctrl+P key’s. A new pop-up window in displayed in which, by default, as a smallimage the captured form is visible. Then, use the “Print” button to print the image on your defaultprinter or use “Save” to save the image as a bitmap file.

The following function/buttons are available

- Form To capture the last active 4nec2 form/window. (first select window, then use button)- Window To capture any other (none 4nec2) window. (click button first, then select window)- Screen To capture the whole screen.

- Clear To clear the captured image- Sel. To switch to full-size image and select partial image to print/save

- Print To print the captured image on your default printer- Save To save the captured image as a bitmap (*.bmp) file

- Copy Copy the image to the clipboard.- Paste Paste an image from the clipboard for printing or saving.

When “Window” is selected you will have to activate/select the window you would like to capture forprinting or saving. After the message-box is closed you will have to seconds to do so.

When you captured a complete form/window or screen and would like to print/save only part of thisimage, use the ‘Sel’(ect) button. The image will change to full-size and while pushing the left-mousebutton you can select any part of the image for printing or saving. Use ‘Res’(et) to reset the selectionand/or try again.

When using Hewlett-Packard (HP) LaserJet Series II printers it is possible that a general protectionfault is generated or that only a blank page is printed. To eliminate this problem, reset the color depthof the video driver on your System to 256 colors or less, or 8 bits per pixel or less. You can do this bychanging the display properties (Click left mouse button on blank part of your desktop)

You can also use the gnuplot program to directly print 2D and/or 3D graphs/plots through the ‘plot’menu-option/command.

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gnuplot The gnuplot plotting program

In version 5.4.0 and later the use of a separate freeware plotting program called ‘gnuplot’ was addedto the 4nec2 package. The gnuplot program is used by 4nec2 to plot and print 2D and 3Dcharts/graphs for various data available through the “plot” menu-bar option on the “Geometry (F3)”,“Pattern (F4)”, “Line- chart (F5)” windows and through the “plot” button on the “Optimizer (F12)”window.

However, before 4nec2 is able to use the gnuplot program, it has the be downloaded from the Internetat http://www.gnuplot.info/download.html and installed on your system. After this the gnuplot maindirectory/folder path has to be specified in 4nec2 by selecting “Setting -> Folders -> gnuplot” on the“Main (F2)” window. See Settings for additional info.

When a plot request is made for a certain data-item two additional windows are displayed. The“plotting options” window in which a number of plot-options can be changed and the “gnuplot graph”window itself in which the resulting graph(s) is/are displayed.

In the “gnuplot graph” window (which belongs to the gnuplot program), when a 2D graph is displayedyou can use the right mouse-button to zoom-in on the graph. Use the “u” key to unzoom and/or reset.When a 3D graph is displayed you can use the left mouse-button to rotate the graph.

To print the current plot/graph click on the graph icon located on the left at the title-bar for the “gnuplotgraph” window and select ‘Options->Print”

In the “plotting options” window you can set/switch the following plotting options:

General options:

- Color To switch plotting color(s)- Line-width To change the width of the plotted lines and/or points- Style To switch between different plotting styles- Point-type To switch point-types for ‘points’ and ‘linespoints; plotting-style- Smooth To ‘smooth’ the graph by selecting a smoothing algorithm.- Grid-lines To enable/disable the grid-lines display.

- Open plot To open/load a previously saved plot/graph.- Add plot To add a previously saved plot/graph to the current plot.- Save plot To save the current plot/graph for future use.- Rem plot To remove/delete the last added plot/graph from the current plot.

2D options

- Log X-axis To switch between a linear or logarithmic X-axis - Log Y-axis To switch between a linear or logarithmic Y-axis - Double Y-axis single(left) or double(left+right) Y-axis when two or more plots loaded- Y2 or Y1 grid To switch between left(Y1)- or right(Y2) Y-axis grid-lines.

3D options

- View as map To switch between a 3D or a 2D map-view.- Size To change the size of the 3D or map-view.- Show surface To switch between grid- or a closed-surface 3D style.- Log Z-axis To switch between a linear or logarithmic vertical Z-axis - Contour plot To display contour lines on the 3D or map-view- Nr cont To change the number of contour lines to display.

- Surface colors To switch between color mapping styles.- Color style To select between different color maps.- Make surface To create full 3D surface when only limited (scattered) 3D data is available

All plotting commands generated by 4nec2 are send to gnuplot through a third (normally minimized)command window “gnuplot”. You can open/restore this window in case of problems and/or if you arecurious about the commands used. But before doing so, I would suggest to first consult the gnuplothelp-files available in the ‘..\gnuplot\doc’ folder.

For those interested in the effectiveness of the optimization algorithms used by 4nec2 it is possible touse the ‘plot’ button after an optimization run (hill-climb or genetic) is done and visualize the searchresults or 3D search-space….

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POVRAY Generate true 3D views

With this feature you are able to generate true 3D views for your geometry structure or the far fieldradiation pattern.This feature works in conjunction with the Povray ray-tracing software, freely available on the internet at http://www.povray.com/

The povray files are generated under the “..\4nec2\pov” folder. These files are based on the defaultpovray file named default.pov under the “..\4nec2\exe” folder. In this default file the settings for the lightsource and the camera position are described. For the more experienced povray users it is possible tomodify this default file to get other light or camera settings.

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DBW and dBuV to S-meter conversion

The following table shows how S DBW (median signal power expected at the receiver inputterminals) values can be mapped to S meter readings. There are a few assumptions: the receiverinput impedance is 50 Ohms and the transmission lineloss is minimal. Also we assume that the Smeter is correctly calibrated. In practice, S meters are mostly imprecise and can only give relativereadings. (dB values are rounded to integer numbers)

S DBW DBuV microvolts S Meter-64 74 4050 S9+40 dB-73 65 1350 S9+30 dB-83 55 450 S9+20 dB-93 44 150 S9+10 dB

-103 34 50 S9-109 28 25 S8-115 22 12.5 S7-121 16 6.25 S6-127 10 3.13 S5-133 4 1.56 S4-139 -2 0.78 S3-145 -8 0.39 S2-150 -14 0.20 S1

For ease-of-use one could use the below approximation:

S9 equals 34 dBuVS9 equals –103 DBWeach 6 dB less equals one S-point

Equations to Calculate The Median Voltage at the Input of the Receiver

Ohm's Law:

E = I*R or I = E/R

Power formula:

P = EI

P is in Watts, E is in Volts and I is in Amps and R is in Ohms. Then:

P = E * [E/R] = (E^2)/R

Solve for Voltage:

E^2 = [P*R]

Convert to dB:

10 Log E^2 = 20 Log E = 10 Log [P*R]

Express E in terms of microVolts such that E(V) = E (uV) x 10^6, then:

20 Log E + 20 Log [ 1V / 10^6] = 10 Log [P*R]

E(dBuV) - 120 = 10 Log P + 10 Log R

Assume R = 50 Ohms:

E(dBuV) - 120 = 10 Log P + 10 Log (50 Ohms) = P(dBW) + 17

E(dBuV) = P(dBW) + 17 + 120 = P(dBW) + 137

Finally, E in uV is 10^(dBuV/20) or antilog [(dBuV)/20]. Example: 35 dBuV = 10^(35/20) = 56 uV.

NOTE: VOACAP computes the signal power [S DBW] which is equivalent to the P(dBW) in theabove equations. DO NOT confuse the predicted field strength in the VOACAP output, DBU (dBrelative to 1 microVolt per meter), with the voltage at the receiver as given by dBuV (dB relative to1 microVolt) in the above equations.

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Ground types

Below some various ground types with their conductivity and dielectric constant are given. Thesevalues can be used when specifying the GN card for the types 0 (finite ground) and 2(Sommerfeld-Norton)

Note: When using GN type 2, the required ground file is automatically generated

GN card, soil Description: Conductivity Permittivity Rel-Quality In S/m (Diel-const.)

Salt water 5.0 81Fresh water 0.001 80Pastoral, low hills, rich soil, typical fromDallas, TX, to Lincoln, NE 0.0303 20 Very GoodPastoral, low hills, rich soil, typical of OHand IL 0.01 14 GoodFlat country, marshy, densely wooded, typicalof LA near the Mississippi River 0.0075 12Pastoral, medium hills, and forestation, typicalof MD, PA, NY (exclusive of mountains andcoastline) 0.006 13Pastoral, medium hills, and forestation, heavyclay soils, typical of central VA 0.005 13 AverageRocky soil, steep hills, typically mountainous 0.002 12-14 PoorSandy, dry, flat, coastal 0.002 10Cities, industrial areas 0.001 5 Very PoorCities, heavy industrial areas, high buildings 0.001 3 Extremely Poor

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Wire conductivity

Below a wire conductivity table to be used for LD card type 5, wire loading

Material Conductivity S/m

Perfect 9.9e99 (lossless)Silver 6.29e7Copper 5.80e7Pure Alumin.3.77e7Al. 6063-T832 3.08e7Al. 6061-T6 2.49e7Brass 1.56e7Phospor bronze 9.09e6Stnlss Stl 302 1.39e6

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AWG Copper Wire Table

AWG Copper Wire Table, converted to metric units.

Note: To get wire radius, divide Diameter by 2.

Diameter Area Ohms per Meters Meters Max.I AWG (mm) (mm^2) 1000 m per kg per ohm (A)

0000 11.6840 136.5159 0.1608 1.05 6217.9 0.0000 000 10.4038 108.2399 0.2028 1.32 4931.7 0.0000 00 9.2659 85.8573 0.2556 1.66 3910.6 0.0000 0 8.2525 68.1031 0.3225 2.10 3102.9 0.0000 1 7.3482 53.9963 0.4065 2.65 2459.7 0.0000 2 6.5430 42.8114 0.5128 3.34 1950.7 22.0000 3 5.8268 33.9511 0.6463 4.22 1546.9 17.5000 4 5.1892 26.9280 0.8153 5.31 1226.8 13.8000 5 4.6203 21.3468 1.0279 6.70 972.9 11.0000 6 4.1148 16.9316 1.2963 8.45 771.4 8.7100 7 3.6652 13.4338 1.6345 10.65 611.7 6.9100 8 3.2639 10.6530 2.0610 13.43 485.2 5.4800 9 2.9058 8.4434 2.5988 16.94 384.7 4.3500 10 2.5883 6.6991 3.2772 21.36 305.1 3.4400 11 2.3038 5.3074 4.1339 26.94 242.0 2.7400 12 2.0523 4.2120 5.2100 33.96 191.9 2.1700 13 1.8288 3.3445 6.5715 42.83 152.2 1.7200 14 1.6281 2.6508 8.2841 54.00 120.7 1.3700 15 1.4503 2.1035 10.4462 68.08 95.7 1.0830 16 1.2903 1.6649 13.1759 85.87 75.9 0.8530 17 1.1506 1.3239 16.6142 108.29 60.2 0.6810 18 1.0236 1.0478 20.9482 136.56 47.7 0.5390 19 0.9119 0.8315 26.4140 172.21 37.9 0.4270 20 0.8128 0.6606 33.3005 217.12 30.0 0.3370 21 0.7239 0.5240 41.9948 273.78 23.8 0.2690 22 0.6452 0.4162 52.9528 345.22 18.9 0.2120 23 0.5740 0.3295 66.7979 435.31 15.0 0.1700 24 0.5105 0.2607 84.2192 548.98 11.9 0.1330 25 0.4547 0.2067 106.2008 692.18 9.4 0.1056 26 0.4039 0.1631 133.8911 872.78 7.5 0.0853 27 0.3607 0.1301 168.8648 1100.37 5.9 0.0672 28 0.3200 0.1024 212.9265 1387.71 4.7 0.0530 29 0.2870 0.0824 268.4711 1750.25 3.7 0.0148 30 0.2540 0.0645 338.5827 2206.78 3.0 0.0333 31 0.2261 0.0511 426.8373 2782.81 2.3 0.0270 32 0.2032 0.0413 538.3858 3509.23 1.9 0.0213 33 0.1803 0.0325 678.8058 4424.97 1.5 0.0163 34 0.1600 0.0256 855.9711 5579.05 1.2 0.0128 35 0.1422 0.0202 1079.3963 7035.91 0.9 0.0000 36 0.1270 0.0161 1360.8924 8868.74 0.7 0.0000 37 0.1143 0.0131 1716.2073 11184.95 0.6 0.0000 38 0.1016 0.0103 2164.0420 14105.39 0.5 0.0000 39 0.0889 0.0079 2729.0026 17791.19 0.4 0.0000 40 0.0787 0.0062 3441.6010 22430.33 0.3 0.0000

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Genetic Algorithms

Genetic algorithms (GA’s) are stochastic search methods that mimic the metaphor of naturalbiological evolution. These algorithms operate on a population of potential solutions applying theprinciple of survival of the fittest to produce better and better approximations to a solution. At eachgeneration, a new set of approximations is created by the process of selecting individualsaccording to their level of fitness in the problem domain and breeding them together usingoperators borrowed from natural genetics. This process leads to the evolution of populations ofindividuals that are better suited to their environment than the individuals that they were createdfrom, just as in natural adaptation. Genetic or evolutional algorithms model natural processes,such as selection, recombination and mutation. They work on populations of individuals instead ofsingle solutions.

An individual, also called chromosome, is a solution to a problem. A chromosome is made up of acollection of genes which are simply the parameters to be optimized. An objective function is usedto determine the fitness (relative performance) of an individual.

At the beginning of the computation a number of individuals (the population or collection ofchromosomes) are randomly initialized. The objective function is then evaluated for theseindividuals. The first/initial generation is produced. If the optimization criteria are not met thecreation of a new generation starts. Individuals are selected according to their fitness-rank for theproduction of offspring. Parents are recombined to produce offspring and offspring is thenmutated with a small probability. The fitness of the offspring is then computed. The offspring(together with an optional number of parents to survive into the next generation (elitism)) areinserted into the population replacing the original parents thus producing a new generation. Thiscycle is performed until the optimization criteria are reached.

Selection and Ranking

Selection determines, which individuals are chosen for mating (recombination) and how manyoffspring each selected individual produces. The first step is ranking of individuals according theirfitness. By default linear ranking is used.

Ranking

The population is sorted according to their FOM values. The ranking assigned to each individualdepends only on its position in the individuals rank and not on the actual FOM value. Rank-basedfitness assignment overcomes the scaling problems of the proportional fitness assignment.(Stagnation in the case where the selective pressure is too small or premature convergencewhere selection has caused the search to narrow down too quickly.) Rank-based fitnessassignment behaves in a more robust manner than proportional fitness assignment and is thedefault method used.

If required 'exponential' ranking can be used. The use of non-linear ranking permits higherselective pressures than the default linear ranking method. Exponential ranking requires anadditional 'base'value. With this value the selective pressure is controlled. This value is the basefor the (rank-1) exponent. For base > 1, on average better individuals will be selected, for large'base' values only the best ones.

Common 'base'values are between 1.1 and 1.5. Base values < 1 would benefit below averageindividuals.

The following list shows the recalculated fitness values for exponential ranking for a given base

value:

rank fitness for base: 2 3 .51 1 1 82 2 3 43 4 9 24 8 27 1

Probability as used with the roulette-wheel or SUS selection (see below) equals individual fitnessdivided by the sum of all fitness values.

The actual selection is performed in the next step. Parents are selected according to their fitnessby means of one of the following algorithms:

- Roulette-wheel selection (SSR)- Stochastic Universal Sampling (SUS)- Select Top best percent (truncation)- Tournament selection

Roulette-wheel selection (SSR)

The simplest selection scheme is roulette-wheel selection, also called stochastic sampling withreplacement (SSR). This involves the following technique: The individuals are mapped tocontiguous segments of a line, such that each individual's segment is equal in size to its fitness. Arandom number is generated and the individual whose segment spans the random number isselected. The process is repeated until the desired number of individuals is obtained. Thistechnique is analogous to a roulette wheel with each slice proportional in size to the fitness. Thebelow list gives an example.

Individual: 1 2 3 4Fitness 1 8 2 4 (exp-ranking with base 2)Selection probability 1/16 1/2 1/8 1/4

Stochastic Universal Sampling (SUS)

Stochastic universal sampling provides zero bias and minimum spread. The individuals are againmapped to contiguous segments of a line, such that each individual's segment is equal in size toits fitness exactly as in roulette-wheel selection. Here equally spaced pointers are placed over theline, as many as there are individuals to be selected. Consider N as the number of individuals tobe selected, then the distance between the pointers is 1/N and the position of the first pointer isgiven by a randomly generated number in the range 0 to 1/N. For 4 individuals to be selected,the distance between the pointers is 1/4=0.25 All individuals are selected in a single 'turn of thewheel'.

It is claimed that stochastic universal sampling ensures a selection of offspring, which is closer towhat is deserved, then roulette wheel selection.

Top N percent selection (truncation)

Compared to the previous methods 'Top N percent' selection is a more artificial selection method.It is used by breeders for large populations/mass selection. In Top N percent selection individualsare sorted according to their fitness. Only the best N percent of the individuals are selected forparents. These selected parents are randomly chosen to produce offspring. The parameter is thepercentage of the population to be selected as parents and takes values ranging from 50%-10%.

Tournament selection

In tournament selection a number Tour of individuals is chosen randomly from the population andthe best individual from this group is selected as parent. This process is repeated as often asindividuals to choose. The selected parents are randomly chosen to produce offspring. Anadditional parameter for tournament selection is the tournament size. This takes values rangingfrom 1 - N (number of individuals in population)

If tournament size is 1 this defaults to random selection. A tournament size of N defaults to bestselection. 2 (standard and not very selective ) and 7 (relatively highly selective) are popularvalues.

Using larger tournaments has the effect of increasing the selective pressure, since below averageindividuals are less likely to win a tournament, while above average individuals are more likely towin.

Elitism

One way to ensure that the best individual(s) will increase from one generation to the next is tore-use the best chromosomes from each generation in next one, bypassing the selection,crossover and mutation operators for those chromosomes. This strategy is frequently referred as‘elitism’. Its benefit is obvious, but there may be a cost, namely loss of diversity in the population.If elitism is used the number of best chrom’s re-used in the next population is specified in the‘Chro’s to re-use’ field.

Recombination

Recombination is done through crossover and mutation. After selection has been carried out, theparents to create the new population are known.

The crossover operator is a method of sharing information between chromosomes; it combinesthe features of two parent chromosomes to form two new offspring., with the possibility that goodchromosomes may produce better ones. The crossover operator is not usually applied to allparents. A random choice is made, where the like hood of crossover being applied depends onthe so-called crossover probability. This probability plays a central role in Genetic Algorithms. Itsvalue is mostly set somewhere between 60-90 percent.

The mutation operator arbitrarily alters one or more genes (variables) of a selected chromosomeso as to increase structural variability of the population. The role of mutation in GA’s is that ofrestoring lost or unexplored solutions into the population to prevent the premature convergence ofGA to sub-optimal solutions. It ensures that the probability of reaching any point in search spaceis never zero. Each gene/variable in the chromosome undergoes a random change according themutation probability, which mostly has a value between 1 and 4 percent. For large number ofvariables the lower values could be specified, for fewer variables a higher value could beappropriate.

The below real-value based crossover algorithms are available:

- Arithmic crossover- Heuristic crossover- Blend crossover (BLX)- Simulated binary crossover (SBX)- 1-point crossover- 2-point crossover

- Uniform crossover

Arithmic crossover

With arithmic crossover offspring variables are created at a certain point linear between bothparent values. The position is determined by the 'alpha' parameter. The below equation is used:

offspring1(j) = alpha * parent1(j) + (1-alpha) * parent2(j)offspring2(j) = (1-alpha) * parent1(j) + alpha * parent2(j)

Heuristic crossover

This crossover operator uses the fitness values of the two parents to determine the direction forwhich to create new offspring. The offspring are created according to the following equations:

offspring1(j) = best-parent(j) + Rnd * (best-parent(j) - worst-parent(j))offspring2(j) = best-parent(j)

Rnd = a random value between 0 (inclusive) and 1. The offspring variables are clipped betweenthe variables upper- and lower limits.

Blend crossover (BLX)

With blend crossover a point is chosen randomly on the (extended) interval between both parentvariables. The parameter alpha specifies the amount for which this interval is extended on eitherside of the interval. For example:

parent1 variable : 10, parent2 variable : 20 -> delta interval : 20-10=10

if alpha = 0.5 then the range for offspring random variable selection is between 10-(0.5*delta) = 5 and 20+(0.5*delta) = 25

The below equations are used to create offspring:

gamma = (1+2*alpha) * Rnd - alphaoffspring1(j) = gamma * parent1(j) + (1-gamma)* parent2(j)offspring1(j) = (1-gamma) * parent1(j) + gamma* parent2(j)

Rnd = a random value between 0 (inclusive) and 1. The offspring variables are clipped betweenthe variables upper- and lower limits.

It is claimed that BLX with an alpha parameter of 0.5 performs better than other alpha values.BLX with an alpha value of zero is the equivalent to flat crossover that uniformly samplesoffspring between the two parents.

Simulated binary crossover (SBX)

Simulated binary crossover (SBX) was developed by incorporating the essence of theself-adaption mechanism into the crossover operator. This approach is similar to BLX in thesense that the offspring is created in proportion to the difference between the parents but SBXhas an unique property – that is, solution-points near the parents are more likely to be selected astheir offspring than solution-points distant from the parents An additional parameter, the distribution index is required. This is a nonnegative real number. Alarge value gives a higher probability for creating near parent solutions and a small value ofallows distant solutions to be selected as children solutionsAs an example: 2.0 produces distant- and 5.0 near-parent offspring.

It was reported that a GA with SBX outperformed a GA with BLX – 0.5 on some test functions.

1-point crossover

In 1-point crossover one crossover position k between 1 and N (number of variables) is randomlyselected and the variables exchanged between the individuals about this point, then two newoffspring are produced. Consider the following two individuals with 5 variables each, which willalso be used to illustrate the other types of recombination:

parent1 12.5 88.4 22.6 4.5 33.2parent2 10.5 102.0 15.8 9.2 42.1

The chosen crossover position is: 2After crossover the new individuals are created:

offspring1 12.5 88.4 15.8 9.2 33.2offspring2 10.5 102.0 22.6. 4.5 42.1

2-point crossover

In 2-point crossover two random ''switching' points are chosen between 1 and N and the variablesexchanged between the individuals about both points and again two new offspring are produced.

Uniform crossover

Uniform crossover performs an exchange of variable values between two individuals by loopingthrough all variables from 1 to N and randomly deciding from which of both parents to get thevariable value. The other offspring is created the ‘inverse' way.

parent1 12.5 88.4 22.6 4.5 33.2parent2 10.5 102.0 15.8 9.2 42.1

For each variable the parent who contributes its variable to the offspring is chosen randomly withequal probability. After crossover the new individuals are created:

offspring1 12.5 102.0 22.6 9.2 42.1offpsring2 10.5 88.4 15.8 4.5 33.2

Mutation

After recombination through crossover, offspring undergo mutation. Offspring variables aremutated by the addition of small random values, with low probability. The below real-value basedmutation operators are available:

- Boundary- Uniform- Gaussian- None-uniform

Boundary mutation

A mutation operator that replaces the value of the chosen variable with either the upper or lowerbound for that gene (chosen randomly).

Uniform mutation

With uniform mutation the value for the selected variable is replaced by a random value chosenuniformly from the interval between the user-specified lower- and upper variable bounds.

Gaussian mutation

A gaussian distribution represents a bell-shaped curve around a certain mean value and with acertain width, called the deviation. If a random gaussian number is generated, there is a biggerpossibility that it is generated near the mean value and a smaller possibility that it is generatedfurther away. For a standard-deviation of one and a mean of zero, 68 % of all random values arebetween +1 and –1, between –2 and +2 are 95% of the values and between –3 and +3 are 99.7percent of all values.

With the gaussian mutation operator, an additional ‘sigma’ value is used. The default for this valueis 2, meaning that a deviation value is chosen equally to the difference between theuser-specified upper- and lower gene-bounds devided by 2. Resulting in a possibility of 95percent that the generated value is in range. You may manually change this ‘sigma’ parameter touse other deviations. The ‘mean’ value for the random number equals the current gene-value tomutate.The new variable/gene value is clipped if it falls outside of the lower- or upper-bound for the gene.

If a ‘sigma’ of zero is specified, the actual sigma value is related to the number of generations,ranging from 2 at the start to almost zero at the end; according the below equation:

sigma = 0.5 * 1/ (1+sqrt(generation number))

This will enable a more broad search at the beginning and narrow it at the end of the process.

None-uniform mutation

Another mutation operator that increases the probability that the amount of the mutation will beclose to 0 as the generation number increases. This mutation operator keeps the population fromstagnating in the early stages of the evolution then allows the genetic algorithm to fine tune thesolution in the later stages of evolution. The chosen gene is mutated according to the followingequations:

mutated gene a) gene + delta(gener_nr, MAX-var) for Rnd() < 0.5 or b) gene - delta(gener_nr, var-MIN) for Rnd() >= 0.5

delta(t,Y) = Y * (1 - Rnd ^ ((1- t / max_generations ) ^ b

t = gener_nrb = user parameter specifying degree of dependency on nr of iterations.

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Nec-2/4 Short Reference guide

Fieldnr -> 1 2 3 4 5 6 7 8 9 10 11

Wire geom GW TagNr NrSegs X1 Y1 Z1 X2 Y2 Z2 rad

No ground GE 0 - - - - - -Gnd plane 1 (Mirror struc, current expans, GN required: rad-W blank) Ground -1 (Mirror struct, no current exp, GN required)

Free space GN -1 - - - - - -Finit. gnd 0 W-rad 0 0 diel. cond. radius (changes RP)Perf. gnd 1 - - - - - -Sommerfeld 2 0 0 0 diel. cond. 0

Voltage src EX 0 Tagnr Segnr --XX U-real U-imag Current src 6 Tagnr Segnr --XX I-real I-imag (*)

Nullify LD -1 - - - - - -Serie RLC 0 Tagnr beg-S 0/end R(ohm) L(H) C(F)Paral. RLC 1 Tagnr beg-S 0/end R(ohm) L(H) C(F) Serie RLC 2 Tagnr beg-S 0/end R Xl XcParal. RLC 3 Tagnr beg-S 0/end R Xl Xc Impedance 4 Tagnr beg-S 0/end Z(ohm) 0 0Wire cond. 5 Tagnr beg-S 0/end Y(S/m) 0 0LC trap 6 Tagnr beg-S 0/end coil-Q L(H) C(F) (*)Insul-wire 7 Tagnr beg-S 0/end Diel-c Radius (*)

Trans-line TL Tag-1 Seg-1 Tag-2 Seg-2 Z0 Length G1r G1i G2r G2i

Network NT Tag-1 Seg-1 Tag-2 Seg-2 Y11r Y11i Y12r Y12i Y22r Y22i

Freq-lin. FR 0 steps 0 0 Start St-siz -Freq-log. 1 steps 0 0 Start St-siz -

All curr. PT -2 - - - - - -No curr. –1 - - - - - -Spec curr. 0 Tagnr beg-S 0/end - - -Receiv. pat 1 Tagnr beg-S 0/end - - -

All charg. PQ -1 - - - - - -Spec charg. 0 Tagnr beg-S 0/end - - -

Far Field RP 0 nr-Th nr-Ph XNDA sta-Th sta-Ph siz-TH siz-Ph 0/dist 0/gainadd surf-W 1 nr-Th nr-Ph XNDA sta-Th sta-Ph siz-TH siz-Ph distan. 0/gainGnd cond. 2,3 nr-Th nr-Ph XNDA sta-Th sta-Ph siz-TH siz-Ph 0/dist. 0/gainGnd screen 4 nr-Th nr-Ph XNDA sta-Th sta-Ph siz-TH siz-Ph 0/dist. 0/gainCondit+Scr. 5,6 nr-Th nr-Ph XNDA sta-Th sta-Ph siz-TH siz-Ph 0/dist. 0/gain

Elec. Field NE 0 nr-X nr-Y nr-Z sta-X sta-Y sta-Z Magn. Field NH 0 nr-X nr-Y nr-Z sta-X sta-Y sta-Z

Geometry : XX I1 I2 F1 F2 F3 F4 12 3-5 6-10 11-20 21-30 31-40 41-50Prog ctrl : XX I1 I2 I3 I4 F1 F2 F3 F4 F5 F6 12 3-5 6-10 11-25 16-20 21-30 31-40 41-50 51-60 61-70 71-80

--XX:19: 0=No action, 1=print rel admit. matrix20: 0=No action, 1 print imp’s for freq sweep

XNDA: 17: 0=major/minor axis, 1=vert/hor gain18: 0=no norm. gain, 1-5=norm gain19: 0-power gain, 1=directivity gain20: 0=no averaging, 1=average gain, 2=radiation-efficiency

TL: Multiple ports are connected in parallel

If connected to segment with LD, LD is in series with TL

NW: LC fields: positive -> L in Henry, negative -> C in Farad

Note: - This summary is far from complete. It only lists the most important cards used by the author for hisinitial steps on the antenna-modeling path.- Use the ‘NEC editor’ (See ‘Settings’ option on the ‘Main’ form) or consult the Nec-2 orNec-4user-manual to assist with filling the appropriate positions for the different NEC cards.(*) 4nec2 extension to default ‘NEC-language’

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Information and Troubleshooting

For problems concerning memory-settings or those related to segment/dimension limits and theselected NEC-engine, see Settings

For additional information or troubleshooting, see the _ReadMeFirst.txt text file located in your4nec2 home-folder. Or contact the author (See About)

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About 4nec2

The 4nec2 program initially was made as a home building project because there were no means fordefining a user specified antenna structure with the ItsHF propagation software, but when more andmore features were added it seemed to me that it would be nice if other people could also use theprogram. So the program reached the Internet where it is free for download.

The first version was developed in the year 1995 under the DOS operating System with the Q-basiclanguage. In the following year it was ported to windows-95 and modified to run with the visual basic3.0 version. Unfortunately this visual basic version was based on the older 16-bit operating systemlayout, so real “multi-tasking” was not supported. Version 4.0, was the first 32 bit version. With thisversion the NEC-editor, variables/symbols and the optimizer were included.

Later on, new versions with additional features and possibilities were created such as a real-time 3Dviewer and a graphically based geometry-editor and provisions were added to also read/processNec-4 based in- and output-files. The name 4nec2 however was not changed, but it should now beseen as “for NEC too”, meaning another piece of software to use with NEC.

However, because it's a home building project and I don't have very much time testing all the programfeatures, it is most likely that there are still errors in the program included. If you detect such an error,please contact me, and if possible describe the problem, include your NEC based input file and I willtry to correct the problem and send you an updated version.

If you have any remarks, complaints, questions or suggestions for additional features or would like to add or alter functionality, please don't hesitate to contact me at 4nec2@gmx.net

Unfortionally because of the rapidly increasing amount of Spam and Virusses and thus to avoid deleting your mail as Spam, please include “4nec2 modeller” as the subject !!

Finally I want to thank Raymond Anderson for giving me the opportunity to publish this program on the internet, Livio Cicala for his help with my first steps on 3D-Drawing, Hardy Lau for his extensive support to get 4nec2 work together with Nec-4 based files and all others who contactedme to report bugs, information and/or suggestions.

Greetings from Holland,

Arie Voors.